JP2005123406A - Plasma etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma etching method capable of satisfactorily etching a fluorocarbon film without damaging other films afterwards. <P>SOLUTION: Etching is performed for a substrate whereon a fluorocarbon film, a hard mask for instance an SiCN film, and a resist film pattern are sequentially laminated. Plasma of a CxFy gas (with x and y each being a natural number) for instance CF<SB>4</SB>gas and a noble gas for instance argon gas is applied for etching the hard mask and the fluorocarbon film. In this process, for instance, the exposed part of the hard mask is not totally etched, with a thin film thereof retained unetched. The resist film is etched next, and then etching may be restarted. By using this method, oxygen plasma during the resist film etching process does not land on the fluorocarbon film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for etching a fluorine-added carbon film formed on a substrate for manufacturing a semiconductor device by plasma.

  As a technique for achieving high integration of semiconductor devices, there is a technique of multilayering wiring. In order to take a multilayer wiring structure, an nth wiring layer and an (n + 1) th wiring layer are connected to a conductive layer. In addition, a thin film called an interlayer insulating film is formed in the region other than the conductive layer. A typical example of the interlayer insulating film is a SiO2 film. In recent years, it has been required to lower the relative dielectric constant of the interlayer insulating film in order to further increase the operation speed of the device.

  Due to such a demand, a fluorine-added carbon film (fluorocarbon film) which is a compound of carbon (C) and fluorine (F) has attracted attention. Whereas the relative dielectric constant of the SiO2 film is around 4, the fluorine-added carbon film is extremely effective as an interlayer insulating film because the relative dielectric constant is, for example, 2.5 or less if the type of source gas is selected. It is a membrane. As for the film formation method, the selection of source gases has progressed, and the development of CVD equipment that generates high-density, low-electron-temperature plasma is expected to provide a high-quality film. A practical application of a fluorine-added carbon film is expected as the film.

  On the other hand, as a method for etching a fluorine-added carbon film, a method is known in which oxygen gas and nitrogen gas are turned into plasma and etching is performed using the plasma (Patent Document 1). In this case, oxygen radicals react with carbon. There is a problem that the side wall is removed because the film is in a so-called burned state, and therefore the cross-sectional shape of the groove after etching becomes a shape that swells laterally (undercut).

  As another method, there is known a method in which hydrogen gas and nitrogen gas are turned into plasma and etching is performed using the plasma (Non-Patent Document 2). In this case, hydrogen is added to the side wall of the etched fluorine-added carbon film. The hydrogen enters and combines with fluorine in the film to generate hydrogen fluoride. In the etched recess, a barrier metal film is formed or metal is embedded in the next process. However, when hydrogen fluoride is generated, the barrier metal film or metal is corroded and damaged, and as a result, There is a problem that adhesion with the film is deteriorated.

JP-A-10-144676: paragraph 0010 Materials Research Society Conference Proceedings, Volume V-14, Advanced Metallization Conference in 1998

    The present invention has been made on the basis of such a background, and an object of the present invention is to make it possible to perform good etching on a fluorine-added carbon film and to prevent damage to other films after etching. It is to provide an etching method.

    The present invention is a plasma etching method characterized in that a fluorine-added carbon film formed on a substrate for manufacturing a semiconductor device is etched by plasma of a processing gas containing CxFy (x and y are natural numbers) gas. . As the CxFy gas, for example, CF4 gas, C2F6 gas, C4F6 gas, C3F8 gas, C4F8 gas and the like can be used.

A specific method of the plasma etching method of the present invention is a method in which a fluorine-added carbon film, a hard mask, and a resist film for forming a pattern are laminated in this order, and a substrate for manufacturing a semiconductor device is etched.
Etching and removing the hard mask;
Next, etching and removing the fluorine-added carbon film with plasma of a processing gas containing CxFy (x and y are natural numbers) gas;
And a step of removing the resist film by etching. The hard mask is used to stop etching since the resist film is removed when the resist film is etched by, for example, active species of oxygen, and then the fluorine-added carbon film is also etched. In this method, the process of etching the hard mask uses, for example, plasma of a processing gas containing CxFy (x and y are natural numbers) gas, but plasma of other gases may be used. The process of removing the hard mask by etching is divided into a first stage in which the hard mask is etched to leave a part of the hard mask and a second stage in which the remaining hard mask is removed by etching. The step of etching the resist film may be performed between the first stage and the second stage. The step of etching the resist film is performed by, for example, plasma containing oxygen active species.

  Further, in the step of etching the resist film, after removing the fluorine-added carbon film by etching, a plasma containing active species of oxygen is used, and a bias power is applied to the substrate so that the hard mask which is the base film is exposed to the plasma. In this case, the sputtered material serves as a protective layer for the side wall of the fluorine-added carbon film, so that fluorine is added during etching (ashing) of the resist film. It can suppress that the side wall of a carbon film is etched. Etching of the fluorine-added carbon film may be performed only with plasma of a processing gas CxFy (x and y are natural numbers), but is preferably performed with plasma of a processing gas to which a rare gas is added.

  According to the present invention, the fluorine-added carbon film can be etched in a good shape, and since hydrogen is not used as a processing gas, hydrogen does not enter the surface portion by performing etching, and in the next step There is no risk of damaging the formed film.

  In describing an embodiment of the plasma etching method of the present invention, a preferred plasma processing apparatus used in this method will be described with reference to FIGS. In the figure, reference numeral 1 denotes a processing container (vacuum chamber) made of, for example, aluminum, and a mounting table 2 is provided in the processing container 1. An electrostatic chuck 21 is provided on the surface of the mounting table 2, and the electrode of the electrostatic chuck 21 is connected to a DC power source 23 via a switch 22. In addition, a temperature control medium flow path 24 that is a temperature control means is provided inside the mounting table 2, and the refrigerant that is the temperature control medium from the inflow path 25 passes through the flow path 24 from the outflow path 26. As a result, the semiconductor wafer (hereinafter referred to as a wafer) W which is a substrate on the mounting table 2 is maintained at a predetermined temperature. Further, a high frequency power supply 27 for bias of 13.56 MHz, for example, is connected to the mounting table 2.

  Further, a gas supply unit 3 made of a conductor whose planar shape is formed in a substantially circular shape, for example, is provided above the mounting table 2, and a number of gases are provided on the surface of the gas supply unit 3 facing the mounting table 2. A supply hole 31 is formed. For example, as shown in FIG. 2, a lattice-like gas flow path 32 communicating with the gas supply hole 31 is formed inside the gas supply section 3, and a gas supply path 33 is connected to the gas flow path 32. Has been. A gas supply source (not shown) is connected to the gas supply path 33, and from each gas supply source, for example, CF4 gas which is CxFy (x and y are natural numbers) gas, for example, Ar (argon) gas which is a rare gas, O 2 (oxygen) gas and N 2 (nitrogen) gas are supplied into the processing container 1 through the gas supply path 33 and the gas supply hole 31.

  In addition, a large number of openings 34 are formed in the gas supply unit 3 so as to penetrate the gas supply unit 3 as shown in FIG. The opening 34 is for allowing plasma to pass through the space below the gas supply unit 3, and is formed, for example, between the adjacent gas flow paths 32. An exhaust pipe 11 is connected to the bottom of the processing vessel 1, and a vacuum exhaust means (not shown) is connected to the base end side of the exhaust pipe 11. Furthermore, an enclosure member (wall portion) 13 provided with a heater 12 as a heating means is provided on the inner surface side of the inner wall of the processing container 1.

  A plate (microwave transmission window) 4 made of a dielectric material such as quartz is provided on the upper side of the gas supply unit 3, and the antenna unit is in close contact with the quartz plate 4 on the upper side of the quartz plate 4. 5 is provided. The dielectric plate is not limited to quartz but may be alumina or the like. As shown also in FIG. 3, the antenna unit 5 is a flat antenna body 50 having a circular planar shape, and a disk-shaped plane provided on the lower surface side of the antenna body 50 and formed with a number of slots. An antenna member (slot plate) 51 is provided. The antenna body 50 and the planar antenna member 51 are made of a conductor and connected to the coaxial waveguide 41. In this example, the antenna main body 50 is divided into two members, and a refrigerant reservoir 52 through which refrigerant flows is formed inside through an external refrigerant flow path (not shown).

  Further, between the planar antenna member 51 and the antenna body 50, there is provided a slow phase plate 53 made of a low-loss dielectric material such as alumina, silicon oxide, silicon nitride or the like. The retardation plate 53 is for shortening the wavelength in the waveguide 41 by shortening the wavelength of the microwave. In this embodiment, a radial line slot antenna (RLSA) is constituted by the antenna body 50, the planar antenna member 51, and the slow phase plate 53.

  The antenna unit 5 configured as described above is attached to the processing container 1 via a seal member (not shown) so that the planar antenna member 51 is in close contact with the quartz plate 4. The antenna unit 5 is connected to an external microwave generating means 42 via a coaxial waveguide 41 so that, for example, a microwave having a frequency of 2.45 GHz or 8.4 GHz is supplied. The waveguide 41 </ b> A outside the coaxial waveguide 41 is connected to the antenna body 50, and the center conductor 41 </ b> B is connected to the planar antenna member 51 through an opening formed in the slow phase plate 53.

  The planar antenna member 51 is made of, for example, a copper plate having a thickness of about 0.3 to 1 mm, and a plurality of slots 54 for generating, for example, circularly polarized waves are formed as shown in FIG. The slot 54 includes a pair of slots 54a and 54b arranged in a substantially T-shape and slightly spaced apart from each other, and is, for example, concentrically or spirally along the circumferential direction around the central portion of the planar antenna member 51. Is formed. Note that the slots 54 may be arranged slightly spaced apart in an approximately eight shape. As described above, since the slots 54a and 54b are arranged so as to be substantially orthogonal to each other, circularly polarized waves including two orthogonal polarization components are radiated. At this time, by arranging the slot pairs 54 a and 54 b at an interval corresponding to the wavelength of the microwave compressed by the retardation plate 53, the microwave is radiated from the planar antenna member 51 as a substantially planar wave.

  More specifically, in this example, the slot length of each of the slots 54a and 54b is equal to or greater than 1/2 the wavelength of the microwave on the coaxial waveguide 41 side in the planar antenna member 51, and the planar antenna member. 51 is set to a size smaller than ½ of the wavelength of the microwave on the plasma generation space (inside the processing vessel 2) 51, the microwave enters the plasma space through the slot 54, and the coaxial waveguide from the plasma space It does not return to the 41 side. The slot may be formed so that the microwave is radiated not by circular polarization but by linear polarization.

  Next, an example of an etching process performed by the plasma processing apparatus, which is a part of the semiconductor device manufacturing process, will be described. As shown in FIG. 4A, a wafer W, which is a substrate for manufacturing a semiconductor device, has a hard mask 62 made of, for example, SiCN on a fluorine-added carbon film (CF film) 61 to be etched. And a resist film (resist pattern) 63 for forming a pattern is formed thereon. A fluorine-added carbon film 65 is formed under the fluorine-added carbon film 61 via a hard mask 64. That is, in this example, the fluorine-added carbon films 65 and 61 correspond to the n-th and n + 1-th interlayer insulating films, respectively. The fluorine-added carbon films 65 and 61 and the hard mask 62 are all formed by CVD using plasma generated by microwaves. The film thickness of the fluorine-added carbon films 65 and 61 is, for example, 5000 mm. The film thickness of the hard mask 62 is, for example, 1000 mm.

  First, the wafer W is loaded into the processing container 1 from the load lock chamber (not shown) through the transfer port not shown in FIG. 1 and placed on the mounting table 2. Subsequently, while supplying CF 4 gas and Ar gas from the gas supply unit 3 at a predetermined flow rate, the inside of the processing vessel 1 is evacuated and maintained at a predetermined pressure, and from the microwave generating unit 42, for example, 2.45 GHz, A high frequency (microwave) of 1500 W is supplied, and a high frequency power for bias of, for example, 13.56 MHz and 1250 W is supplied from the high frequency power supply unit 27 to the mounting table 2.

  The microwave propagates in the coaxial waveguide 41 in the TM mode, the TE mode, or the TEM mode, reaches the planar antenna member 51 of the antenna unit 5, and passes through the central conductor 42 </ b> B of the coaxial waveguide 41. While propagating radially from the central portion of the antenna member 51 toward the peripheral region, microwaves are emitted from the slot pairs 54 a and 54 b toward the lower space via the quartz plate 4.

  At this time, since the slot pairs 54a and 54b are arranged as described above, circularly polarized waves are uniformly emitted over the plane of the planar antenna member 51, and the electric field density in the processing space below is made uniform. On the other hand, CF 4 gas and Ar gas flowing out from the gas supply unit 3 into the processing container 1 diffuse through the opening 34 (see FIG. 2) of the gas supply unit 3 to the upper side, and are plasma by the microwave energy. Is excited. Then, the plasma flows into the processing space below the gas supply unit 3 through the opening 34, and the exposed hard mask 62 is first etched by the active species in the plasma. The etching of the hard mask 62 is considered to cause the CF compound to adhere to the surface and be removed together with this compound, as can be estimated from the experimental examples described later.

  Then, as shown in FIG. 4B, before all the hard mask 62 is etched, for example, when the film thickness of the hard mask 62 becomes about 1/4 of the original film thickness, gas supply and power supply are performed. The process is temporarily stopped to switch to an etching (ashing) process of the resist film 63. This etching process is performed by supplying Ar gas, O 2 gas, and N 2 gas from the gas supply unit 3 into the processing container 1, emitting microwaves from the planar antenna member 51, and supplying high frequency bias to the mounting table 2. Is called. The mixed gas is turned into plasma by microwave energy, and the resist film 63 is ashed and removed by oxygen radicals that are oxygen active species in the plasma (FIG. 4C).

  Thereafter, the gas supply and power supply are stopped, the process is temporarily stopped, and the process is switched to the etching process of the fluorine-added carbon film 61. This etching process is performed under the same conditions as when the hard mask 62 was etched. The etching mechanism is presumed from the following experimental examples, and F active species and CF active species are generated in the plasma, and these active species react with the fluorine-added carbon film 61, and the film is volatile such as CF2 and CF3. It is thought that it will be removed as a natural gas. Thus, the fluorine-added carbon film 61 is etched, and the underlying hard mask 64 is exposed as shown in FIG.

  According to the above-described embodiment, as will be apparent from experimental examples described later, a favorable shape, that is, an etching shape with high perpendicularity, can be obtained as the etching shape of the fluorine-added carbon film 61. Since, for example, CF4 gas, which is CxFy gas, is used and hydrogen gas is not used, hydrogen enters the sidewall surface of the concave portion of the fluorine-added carbon film formed by etching due to the etching. There is no such thing. For this reason, there is no possibility of damaging the barrier metal film formed in the recess in the next step or the metal film embedded in the recess, and the expected electrical characteristics can be obtained.

In addition, since the selection ratio which is the ratio of the etching rate of the fluorine-added carbon film 61 to the etching rate of the SiCN film 62 which is a hard mask can be increased, the exposed hard mask 62 is left thin without being etched. A method of etching the resist film 63 and then etching the remaining hard mask 62 and the fluorine-added carbon film 61 can be employed. For this reason, since the plasma of oxygen gas is not irradiated to the fluorine-added carbon film 61 during the etching of the resist film 63, the above-described undercut (the side wall swells and is etched) does not occur,
Therefore, it is possible to obtain a good etching shape with higher verticality.

  In addition, according to the plasma processing apparatus described above, circularly polarized waves are emitted uniformly over the plane of the planar antenna member 51, the electric field density in the processing space below is uniformized, and wider due to microwave energy. A dense and uniform plasma is excited over the entire processing space, so that uniform processing can be performed at a high etching rate.

  Further, another embodiment of the present invention will be described with reference to FIG. In this embodiment, a wafer having a surface structure similar to that used in the previous embodiment (FIG. 5A) is used, and CF4 gas and Ar gas are converted into plasma and etched. However, the etching of the hard mask 62 is completely stopped without stopping (FIG. 5B), and the fluorine-added carbon film 61 is continuously removed by etching (FIG. 5C). . Thereafter, while generating plasma containing oxygen active species, for example, while generating plasma of Ar gas, N2 gas and O2 gas, a bias power of about 500 W to 1000 W, for example, is applied to the mounting table 2 to apply the resist film 63. Etching is performed.

  In this embodiment, the resist film 63 is etched (ashed) and removed by the active species of oxygen. Further, if Ar ions sputter the hard mask 64 which is the base film of the fluorine-added carbon film 61 and the sputtered material adheres to the side wall of the concave portion of the fluorine-added carbon film 61, it plays the role of a protective film. However, the action of etching the side wall is suppressed. As a result, the concave portion does not become an undercut shape, and a good shape can be maintained. In this embodiment, other rare gas may be added instead of Ar gas.

  In the above, the CxFy gas used in the present invention is not limited to CF4 gas, and C2F6 gas, C3F8 gas, C3F9 gas, C4F8 gas, and the like can be used. The hard mask is not limited to the SiCN film but may be an insulating film such as a SiO 2 film, a SiOF film SiCO, a SiCOH, or a Si 3 N 4 film, and these insulating films can be etched with CxFy gas such as CF 4 gas. Furthermore, the hard mask may be a conductive film such as TiN or TiW instead of the insulating film. In this case, for example, BCl3 plasma can be used as a gas for etching the hard mask.

  The step of removing the resist film 63 by etching is preferably performed with the hard mask 62 remaining, but is performed after removing the hard mask 62 and further removing the fluorine-added carbon film 61 by etching. Also good. The rare gas used when etching the fluorine-added carbon film 61 is not limited to Ar gas, but may be Xe gas or Kr gas.

The results of experiments conducted to confirm the effects of the present invention will be described below.
(A. Electron density in plasma processing equipment)
Ar gas is supplied into the processing chamber 1 of the plasma processing apparatus of FIG. 1, the pressures are set to 6.7 Pa, 67 Pa, and 133 Pa, the microwave power is set to 2000 W, and the position is 60 mm below the quartz plate 4. The electron density was measured using a Langmuir probe. The results are as shown in FIG. Note that zero on the horizontal axis corresponds to the center position on the mounting table 2. As can be seen from this result, the electron density is about 1 × 10 ¹² (pieces / cm 3), which is about 10 times larger than that of the parallel plate type plasma apparatus. Also, it can be seen that the electron temperature is 1.5 eV at the same position, so that high density and low electron temperature plasma can be obtained.
(B. Composition change of fluorine-added carbon film by etching)
The case where a mixed gas of CF4 gas and Ar gas (Ar gas / CF4 gas) is used as a processing gas for etching the fluorine-added carbon film, and the H2 gas and N2 described in Non-Patent Document 2 described above. The difference in the composition of the side wall surface of the recess formed by etching was evaluated for the case of using a gas mixture gas (H2 gas / N2 gas). The evaluation method does not use the wafer having the laminated film shown in FIG. 4, but forms a fluorine-added carbon film on the entire wafer surface, carries this substrate into the plasma processing apparatus, and the bias is Plasma was generated using two kinds of processing gases without applying them, and etching of the fluorine-added carbon film was performed. As the processing gas, H 2 gas / N 2 gas whose flow rate was set to 200/200 sccm and Ar gas / CF 4 gas whose flow rate was set to 400/100 sccm were used. At this time, the microwave power is set to 2000 W, the pressure is set to 1.33 Pa (10 mTorr), and the plasma irradiation time is 30 seconds. Since accelerated ions do not collide with the side wall of the recess formed by actual etching, etching was performed without applying a high frequency bias to the mounting table 2 in order to model the side wall.

  Then, the surface portion of the fluorine-added carbon film before etching, the surface portion of the fluorine-added carbon film when etched with (H2 gas / N2 gas), and the etching with (Ar gas / CF4 gas) When the bonding state of CF was examined by XPS (X-ray photoelectron spectrometer) on the surface portion of each of the fluorine-added carbon films, the results shown in FIGS. 7A to 7C were obtained.

  When H2 gas / N2 gas is used, CF2 and CF3 decrease as shown in FIG. 7B, whereas CC or C-H, as compared to the profile before processing shown in FIG. 7A. It can be seen that the coupling of increases. Therefore, when the penetration depth of H (hydrogen) into the film was examined on the surface portion by RBS (Rutherford backscattering), the result shown in FIG. 8 was obtained. As can be seen from this result, the concentration of H atoms is increased by about 2.5 times at a depth of about 1000 mm from the outermost surface by irradiation with H2 gas / N2 gas plasma. Although not shown in FIG. 8, N (nitrogen) atoms were only observed on the outermost surface and did not penetrate into the fluorine-added carbon film. On the other hand, since hydrogen has a small atomic radius, it is assumed that hydrogen easily enters and diffuses into the film. Therefore, it was found that hydrogen can penetrate deeply into the film by simply irradiating the fluorine-added carbon film with hydrogen plasma and change the film composition.

On the other hand, when Ar gas / CF 4 plasma is irradiated, the profile of the CF bonding state on the surface of the film hardly changes as shown in FIG. It was confirmed that there was no risk of hydrogen damage.
(C. Relationship between flow ratio of Ar gas / CF4 gas and etching characteristics)
In order to investigate the etching mechanism of the fluorine-added carbon film with CF4 gas, first, the relationship between the flow rate ratio of Ar gas / CF4 gas and the etching rate was examined, and the result shown in FIG. 9 was obtained. For other process conditions, the microwave power and bias power are 1500 W and 1250 W, respectively, the pressure is 1.33 Pa, and the wafer temperature is 40 ° C.

As can be seen from FIG. 9, the etching rate is slow when the flow rate of CF4 gas is small, and the etching rate increases rapidly as the amount of CF4 gas added is increased. Ar gas alone has only a sputtering effect, etching by chemical reaction does not occur at all, and C (carbon) is generally known to have a high adsorption coefficient and F (fluorine) is highly volatile. Since the fluorine-added carbon film has a C / F ratio of about 1 and a high C ratio, it is considered that gasification does not occur only by sputtering. By adding CF4, etching species such as F and CF are generated in the plasma and the fluorine-added carbon film is etched, and the film surface part is desorbed as a volatile gas such as CF2 and CF3. Is presumed to have been promoted.
(D. Relationship between high frequency power and etching characteristics)
When the constant velocity line was obtained by plotting the point at which the etching rate of the fluorine-added carbon film was equal while changing the microwave power and the bias power, the result shown in FIG. 10 was obtained. Other process conditions are described in item C.1 above. D. The conditions are the same as described in. As can be seen from this result, the etching rate increases when either the microwave power or the bias power is increased, and in particular, increases rapidly when the microwave power is increased. This is considered to be due to the fact that the dissociation of CF4 is promoted by the high-density plasma and the amount of etching species is increased.

  Similarly, when an isokinetic line of the etching rate was obtained for the SiCN film as a hard mask, the result shown in FIG. 11 was obtained. It can be seen that the etching speed of the SiCN film differs greatly from the plasma density and greatly depends on the bias power, unlike the fluorine-added carbon film. From this result, it can be said that the etching of the SiCN film is dominated by the ion sputtering energy rather than the ion density. FIG. 12 is a map connecting point groups that are equal in selectivity ratio (etching rate of fluorine-added carbon film / etching rate of SiCN film) derived from the relationship of FIGS. 10 and 11. It has been found that the conditions for etching the fluorine-added carbon film at high speed and obtaining a high selectivity require microwave power, that is, high-density plasma, and hardly depend on the bias power. Therefore, it can be understood from the result of FIG. 6 that the plasma processing apparatus shown in FIG. 1 is effective as an apparatus for etching the fluorine-added carbon film.

(E. Relationship between wafer temperature and etching characteristics)
The microwave power and bias power are set to 1500 W and 1250 W, respectively, the pressure is set to 1.33 Pa, the flow rate of Ar gas / CF 4 gas is set to 400/100 sccm, and the wafer temperature is set to 0 ° C. and 40 ° C. When the effect on the selection ratio and the angle of the side wall of the etched recess was examined with two settings, the results shown in FIGS. 13 and 14 were obtained.

  As can be seen from FIG. 13, the selectivity increases as the wafer temperature increases. This is because the etching rate of the SiCN film decreases as the wafer temperature rises. That is, it is considered that the amount of deposition (deposits) on the surface of the SiCN film at the time of etching decreased with the increase in wafer temperature, thereby suppressing the etching reaction. Here, if the deposit acts as a protective film, the deposit becomes thinner and the etching rate of the SiCN film increases as the wafer temperature rises, and the selectivity should decrease. Therefore, the etching mechanism of the SiCN film is not the deposit attached to the surface of the SiCN film acting as a protective film, but the CF compound is deposited on the surface of the SiCN film like the etching mechanism of SiO2, and the deposit It is presumed that the SiCN film is peeled off together with the substrate.

As can be seen from FIG. 14, when the wafer temperature increases, the angle of the side wall of the recess with respect to the wafer surface approaches perpendicularly. This seems to be a general reaction in which the etching product is exhausted without being adsorbed on the side wall of the etched portion as the temperature rises.
(F. Observation of etching shape and etching with other processing gas)
The microwave power and bias power were set to 1500 W and 1250 W, respectively, the pressure was set to 1.33 Pa, the Ar gas / CF 4 gas flow rate was set to 400/100 sccm, and the wafer temperature was set to 40 ° C. First, the SiCN film, which is a hard mask formed on the fluorine-added carbon film, was removed by etching, and then the fluorine-added carbon film was etched. The film thicknesses of the fluorine-added carbon film and the hard mask are 5000 mm and 1000 mm, respectively. This process is referred to as Example F-1.

  C4F8 gas is used instead of CF4 gas, Ar gas and O2 gas are used, the flow rate of Ar gas / C4F8 gas / O2 gas is set to 1000/15/10 sccm and the pressure is set to 2.66 Pa. Etching was performed in the same manner as in Example F-1. This process is referred to as Example F-2.

  Etching was performed in the same manner as in Example F-2 except that N2 gas was used instead of O2 gas. This process is referred to as Example F-3.

  When the cross section of the recess obtained in Example F-1 was confirmed by SEM (scanning electron microscope), the shape shown in FIG. 15 was obtained, and the side wall angle θ was as high as 87 degrees. Moreover, it was the same result also about Example F-2 and Example F-3. The etching rate (etch rate) and the selection ratio in each example were as follows. The unit of etching is Å / min.

Etch rate of CF film Etch rate of SiCN film Selectivity Example F-1 10040 2090 4.8
Example F-2 3274 496 6.6
Example F-3 2301 318 7.2
(G. Effect of resist film etching on fluorine-added carbon film)
After removing the fluorine-added carbon film as in Example F-1, Ar gas, N2 gas, and O2 gas were supplied into the processing vessel at flow rates of 400 sccm, 100 sccm, and 50 sccm, respectively, and the pressure was set to 2.66 Pa. Then, the microwave power and the bias power were set to 1500 W and 500 W, respectively, and the temperature of the wafer was set to 40 ° C., and the resist film was etched and removed. When the shape of the concave portion of the fluorine-added carbon film was examined, the shape was almost the same as that before etching of the resist film, and no undercut occurred. This example is an experiment corresponding to another embodiment shown in FIG. 5, and it can be seen that it is effective to apply a bias power to the mounting table during etching of the resist film.

  From the above experimental results, if the fluorine-added carbon film is etched with plasma of CxFy (x and y are natural numbers) gas, a good recess shape can be obtained, and there is no problem due to the mixing of hydrogen. However, it is proved that a high selection ratio can be obtained.

It is a vertical side view which shows an example of the plasma processing apparatus used for embodiment of this invention. It is a top view which shows the gas supply part used for said plasma processing apparatus. It is a perspective view which shows the antenna part used for said plasma processing apparatus in a partial cross section. It is explanatory drawing which shows a mode that the fluorine addition carbon film concerning embodiment of this invention is etched. It is explanatory drawing which shows a mode that the fluorine addition carbon film concerning other embodiment of this invention is etched. It is explanatory drawing which shows the plasma electron density distribution in said plasma processing apparatus. It is explanatory drawing which shows the analysis result of the XPS of the surface part of a fluorine addition carbon film. It is explanatory drawing which shows the analysis result of RBS of the fluorine addition carbon film plasma-processed using H2 / N2 gas. It is explanatory drawing which shows the relationship between the dilution rate by the Ar gas of CF4 gas, and the etching rate of a fluorine addition carbon film. It is explanatory drawing which shows the map of the etching rate of a fluorine addition carbon film. It is explanatory drawing which shows the map of the etching rate of SiCN which is a hard mask. It is explanatory drawing which shows the map of the selection ratio of a fluorine addition carbon film / SiCN film. It is explanatory drawing which shows the relationship between the temperature of a mounting base, and the selection ratio of a fluorine addition carbon film / SiCN film. It is explanatory drawing which shows the relationship between the temperature of a mounting base, and the inclination of the side wall of a fluorine addition carbon film. It is explanatory drawing which shows the observation result of the recessed part obtained by etching with respect to a fluorine addition carbon film by the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing container 2 Mounting base 27 High frequency power supply part 3 for bias Gas supply part 31 Gas supply hole 4 Quartz plate 41 Coaxial waveguide 42 Microwave generation means 5 Antenna part 51 Planar antenna member 61, 65 Fluorine addition carbon film 62, 64 Hard mask 63 Resist film

Claims (7)

A plasma etching method comprising etching a fluorine-added carbon film formed on a substrate for manufacturing a semiconductor device with a plasma of a processing gas containing CxFy (x and y are natural numbers) gas. In the method of etching a substrate for manufacturing a semiconductor device, a fluorine-added carbon film, a hard mask and a resist film for forming a pattern are laminated in this order.
Etching and removing the hard mask;
Next, etching and removing the fluorine-added carbon film with plasma of a processing gas containing CxFy (x and y are natural numbers) gas;
And a step of etching and removing the resist film. 3. The plasma etching method according to claim 2, wherein the step of etching the hard mask uses a plasma of a processing gas containing CxFy (x and y are natural numbers) gas. The process of removing the hard mask by etching is divided into a first stage in which the hard mask is etched to leave a part of the hard mask, and a second stage in which the remaining hard mask is removed by etching. And
4. The plasma etching method according to claim 2, wherein the step of etching the resist film is performed between the first stage and the second stage. 5. The plasma etching method according to claim 2, wherein the step of etching the resist film is performed using plasma containing oxygen active species. In the step of etching the resist film, after removing the fluorine-added carbon film by etching, a plasma containing active species of oxygen is used, and a bias power is applied to the substrate to form a hard mask as a base film in the plasma. 4. The plasma etching method according to claim 2, wherein the plasma etching method is performed while sputtering with active species. 7. The plasma etching method according to claim 1, wherein the etching of the fluorine-added carbon film is performed by plasma in which a rare gas is added to CxFy (x and y are natural numbers) gas.

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