JP2011071510A - Film forming method, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high barrier properties against elements constituting wiring metal and elements constituting an interlayer insulating film to a barrier film formed between the interlayer insulating film and wiring metal. <P>SOLUTION: A mounting table 51 on which a substrate is mounted and a plane antenna member 82 having many slits formed in a circumferential direction are provided in a processing container opposite each other, and a microwave from a waveguide is supplied into the processing container through the plane antenna member. While a gas for plasma generation such as an Ar gas is supplied into the processing container from above, for example, a trimethylsilane gas and a nitrogen gas as material gas are supplied from a position different from a supply port for the gas for plasma generation to generate a plasma of those gases, and further biasing high-frequency electric power is applied so that biasing high-frequency electric power supplied per unit area of an upper surface of the mounting table 51 may be &le;0.048 W/cm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a technique for forming a barrier film interposed between a wiring metal and an interlayer insulating film in a semiconductor device by plasma.

  For example, when adopting a dual damascene process, a multilayer wiring structure for achieving high integration of a semiconductor device connects a trench for wiring embedding and a lower layer side wiring and an upper layer side wiring to an interlayer insulating film on the lower layer side. For example, a via hole for embedding an electrode is simultaneously formed, a wiring metal such as copper is buried in the trench and the via hole to form a lower layer structure, and such structures are sequentially stacked. In such a structure, it is necessary to prevent the wiring metal from diffusing into the interlayer insulating film, and in particular, when copper is used, it is easy to diffuse, so copper diffusion prevention on the inner wall of the recess including the trench and via hole is prevented. In addition, a barrier film is interposed between the copper wiring in the trench and the interlayer insulating film on the upper layer side.

FIG. 17 schematically shows a part of the structure in which the copper wiring 102 is formed in the trench of the lower interlayer insulating film 101 and the electrode 103 is formed on the copper wiring 102. In the figure, reference numeral 104 denotes a barrier metal formed on the inner wall of a recess made of a trench and a via hole, and 105 denotes a barrier film interposed between the copper wiring 102 and an interlayer insulating film (not shown) on the upper layer side. Here, the barrier metal 104 needs to be conductive because it remains between the upper surface of the copper wiring 102 and the lower surface of the electrode 103 in the manufacturing process. For example, a film containing tantalum, titanium, or the like is used.
On the other hand, since the barrier film 105 is formed on the entire surface of the copper wiring 102 except for the portion where the electrode 103 is formed, the barrier film 105 is interposed between the lower interlayer insulating film and the upper interlayer insulating film and is not shown from the copper wiring 102. Copper is prevented from diffusing into the interlayer insulating film on the upper layer side. In order to avoid an increase in the dielectric constant of the entire interlayer insulating film due to the presence of the barrier film 105, examples of the barrier film 105 include a SiCN film and a SiC film made of silicon (Si), carbon (C), and nitrogen (N). Or amorphous carbon etc. are used, for example, forming into a film by plasma CVD using trimethylsilane gas and nitrogen gas (patent documents 1).

By the way, with the miniaturization of semiconductor devices, there is a demand for further thinning of the barrier film 105. However, if the film is made too thin, the copper in the copper wiring 102 is transferred to the barrier film 105 in an annealing process at, for example, about 400 ° C. And penetrates into the interlayer insulating film, resulting in poor insulation of the interlayer insulating film, leading to an increase in leakage current between the wirings. For these reasons, there is an increasing demand for further improving the denseness of the barrier film so that a high barrier property can be obtained even if the film thickness is reduced.
Recently, a fluorine-added carbon film (fluorocarbon film) that is a compound of carbon (C) and fluorine (F) capable of ensuring a low relative dielectric constant of 2.5 or less, for example, has been adopted as an interlayer insulating film. It is being considered. However, since the fluorine-added carbon film is easily desorbed when heated, when the barrier film is thinned, the fluorine from the fluorine-added carbon film that forms the interlayer insulating film on the upper layer side of the barrier film 105 during the annealing described above. There is a concern that the barrier film 105 may be penetrated and diffused into the copper wiring 102 to increase the wiring resistance.

  Patent Document 2 describes an experiment in which a fluorine-added carbon film is embedded by applying a bias power of 500 W or more to an 8-inch wafer in a plasma apparatus using electron cyclotron resonance. There is no mention about.

JP 2006-294816 A Japanese Patent Laid-Open No. 10-144675: FIG. 19, paragraph 0046

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a film forming method capable of obtaining a high barrier property for a barrier film interposed between a wiring metal and an interlayer insulating film in a semiconductor device. It is to provide. Still another object is to provide a semiconductor device including a barrier film formed by the method of the present invention.

The present invention relates to a method for forming a barrier film interposed between a wiring metal and an interlayer insulating film in a semiconductor device.
A step of placing the substrate on the placement portion in the processing container;
Supplying a film forming gas containing an organic compound and a plasma generating gas for accelerating the plasma formation of the film forming gas into the processing container;
Evacuating the inside of the processing vessel;
Converting the plasma generating gas and the film forming gas in the processing vessel into plasma, and forming the barrier film containing carbon on the substrate by the plasma; and
A step of applying a biasing high-frequency power to the mounting portion while this step is being performed.

As a preferred example of the present invention, the plasma generating gas and the film forming gas are supplied into the processing container from different supply ports, and are provided on the upper part of the processing container so as to face the above-described mounting portion. A method of turning the gas in the processing container into plasma by supplying microwaves into the processing container from a planar antenna member in which a large number of slits are formed along the direction can be given. The high-frequency power for bias supplied to the unit area of the substrate is preferably 0.047 W / cm ² or less.

Further examples of gases and barrier films used in the present invention are listed below.
The film forming gas includes an organic compound gas of silicon, and the barrier film is a film containing silicon.
The barrier film is a SiCN film.
The barrier film is a SiC film.
The barrier film is an amorphous carbon film. In this case, the film forming gas is, for example, butyne gas. The film-forming gas further contains a silane-based gas in addition to butyne gas, and the amorphous carbon film contains silicon.

The gas for generating plasma is argon gas.
An example of the interlayer insulating film is a fluorine-added carbon film that is a compound of carbon and fluorine.

Another invention is a film forming apparatus for forming a barrier film interposed between a wiring metal and an interlayer insulating film in a semiconductor device.
An airtight processing container provided with a placement portion on which a substrate is placed; and
Gas supply means for supplying a film forming gas containing an organic compound and a plasma generating gas for accelerating the plasma formation of the film forming gas into the processing container;
Means for evacuating the inside of the processing vessel;
Plasma generating means for converting the gas in the processing vessel into plasma;
Means for applying high-frequency power for bias to the mounting portion;
A gas for generating plasma and a gas for forming a film containing an organic compound are introduced into the processing container, and these gases are turned into plasma while applying high-frequency power for bias to the mounting portion, and carbon is formed on the substrate. And a control unit for outputting a control command to each unit so as to form a thin film including the thin film.

In a preferred aspect of the present invention, the gas supply means includes a supply port for supplying a plasma generating gas excited by microwaves into the processing container, and the supply port for supplying a film forming gas. Has different supply ports, and
The plasma generating means is connected to the waveguide for guiding the microwave to the upper part of the processing container and the waveguide for supplying the microwave from the waveguide into the processing container. And a planar antenna member provided facing the mounting portion and formed with a large number of slits along the circumferential direction.

Still another invention is a storage medium that stores a computer program that is used in a film forming apparatus and that operates on a computer, and the computer program includes steps for performing the film forming method described in the claims. It is characterized by being rare.
Yet another invention is a semiconductor device comprising a barrier film formed by the film forming method described above.

  According to the present invention, when a barrier film interposed between a wiring metal and an interlayer insulating film in a semiconductor device is formed on a substrate, a film forming gas containing an organic compound and a film forming gas plasma are provided. A high-frequency power for bias is applied to the mounting portion on which the substrate is placed, while forming a barrier film containing carbon on the substrate by converting the plasma generating gas for promoting the formation into a plasma and forming a carbon-containing barrier film on the substrate. Therefore, ions that are active species of plasma generating gas, for example, argon ions, are deposited while colliding with the substrate, and a dense and highly barrier film is obtained due to the collision.

It is process drawing which showed the manufacturing procedure of the semiconductor device containing CF film | membrane of this invention. It is sectional drawing which shows the semiconductor device concerning embodiment of this invention. It is a schematic diagram which shows the mode of the board | substrate when forming the barrier film of this invention. It is explanatory drawing which shows the estimation mechanism of the reaction when a high frequency bias is applied to the wafer W. It is a vertical side view which shows an example of the plasma film-forming apparatus used for embodiment of this invention. It is a top view which shows the 2nd gas supply part used for said plasma film-forming apparatus. It is a perspective view which shows the antenna part used for said plasma film-forming apparatus in a partial cross section. It is a characteristic view which shows the degassing amount about the board | substrate concerning an Example. It is a characteristic view which shows content of the fluorine in the depth direction of the board | substrate concerning an Example, and oxygen. It is a characteristic view which shows the film-forming speed | rate and refractive index of the barrier film concerning an Example. It is a characteristic view which shows the adhesive strength of the barrier film and CF film | membrane concerning an Example. It is explanatory drawing which shows the measuring method of 4 point bending method (strength test). It is explanatory drawing which shows the characteristic data in a 4-point bending method. It is explanatory drawing which shows the result of the said intensity test for every bias electric power applied at the time of SiCN film-forming. It is explanatory drawing which shows the result of the said intensity | strength test at the time of performing a bias plasma process with respect to the surface of CF film. It is explanatory drawing which shows the result of the said intensity | strength test at the time of performing a bias plasma process with respect to the surface of CF film. It is a characteristic view which shows the result of the severe test for evaluating the adhesive strength of the barrier film and CF film concerning an Example. It is a perspective view which shows a part of general multilayer wiring structure.

  An embodiment of a manufacturing method according to a semiconductor device of the present invention will be described with reference to FIG. FIG. 1A shows an nth (lower stage) circuit layer formed on a wafer W having a diameter of 200 mm (8 inches), for example, which is a substrate. A wiring metal 11 made of Cu or the like is embedded in a fluorine-added carbon film (hereinafter referred to as “CF film”) 10. A barrier metal film 12 made of, for example, a tantalum nitride film or a tantalum film is interposed between the CF film 10 and the wiring metal 11 so that, for example, copper does not diffuse from the wiring metal 11 into the CF film 10. . In the following description, the nth and (n + 1) th are referred to as a lower layer side and an upper layer side wiring, respectively.

First, as shown in FIG. 1B, on the surface of the lower circuit layer, in order to suppress degassing components and metal diffusion between the lower circuit layer and the upper circuit layer, For example, the barrier film 13 made of an insulating compound such as SiCN is formed. The barrier film 13 is formed by using, for example, a film formation gas composed of trimethylsilane ((CH ₃ ) ₃ SiH) gas and nitrogen (N ₂ ) gas, which is an organic compound of silicon, and argon (Ar) gas, which will be described later. As described in the apparatus, the film is formed (activated) by microwave energy and supplied to the wafer W heated to 350 ° C., for example. In this example, the argon gas is a plasma generating gas for promoting the plasma formation of the film forming gas, and may be a rare gas such as Kr instead of Ar. It may also be used NH _3, N ₂ O or the like in place of N _2.
When the barrier film 13 is formed, a high frequency of, for example, 2 MHz or less, for example, 800 kHz, which is a frequency range in which ions in plasma can follow the wafer W from a bias high-frequency power source 52 described later, for example, about 10 W, for example. By supplying with electric power, argon ions in the plasma are attracted to the wafer W side. By thus applying the high frequency bias to the wafer W, the barrier property of the barrier film 13 is improved as will be described later. This is presumed to be caused by the fact that the barrier film 13 becomes dense. Therefore, the presumed mechanism for forming the barrier film 13 will be described with reference to FIGS. 3 (a) and 3 (b). First, when the trimethylsilane gas is activated, a part of the bond between carbon (C) and hydrogen (H) is broken in the molecule of trimethylsilane, the bond between silicon and carbon or hydrogen is broken, etc. It is thought that the active species became.

Therefore, as shown in FIG. 3A, when ions of argon gas are attracted to the wafer W side and collide with such active species located near the surface of the wafer W, weak bonds in the active species, for example, C—H The bond is broken and hydrogen is desorbed from the active species, and is present between the remaining carbon and other active species as shown in FIG. 3B or on the surface of the barrier film 13 during the film formation. It is considered that a new bond is formed with the carbon via a dangling bond (unbonded hand) of the carbon.
On the other hand, hydrogen desorbed from the active species becomes hydrogen gas, and is not taken into the barrier film 13 and is discharged from the processing atmosphere. Since such reactions proceed sequentially on the surface of the wafer W, a large number of, for example, carbon-carbon bond networks are formed in the barrier film 13, and these bonds form a network (cross-link). Therefore, it is assumed that the film becomes dense and the hardness of the film increases.

  Further, when argon gas ions collide with the surface of the wafer W, the C—H bond, which is also a weak bond, is cut on the surface of the wafer W (FIG. 3A), and dangling bonds are generated. (FIG. (B)). It is presumed that the reactivity at the site where the dangling bond is generated increases, so that the probability of attachment of active species increases, and as a result, the deposition rate of the barrier film 13 increases. In this way, the barrier film 13 is denser and higher in strength by applying the high frequency bias than in the case where the high frequency bias is not applied, and the film forming speed is also increased.

Next, returning to FIG. 1, as shown in FIG. 1C, a CF film 20 that is an interlayer insulating film is formed on the surface of the barrier film 13. This CF film 20 is formed by converting C ₅ F ₈ gas, which is a film forming gas of a compound containing carbon and fluorine, into plasma together with argon gas, and the flow rate of each gas is, for example, 200 sccm and 300 sccm, and the pressure in the container is 55 mTorr. A film is formed by supplying plasma containing active species of C ₅ F ₈ on a wafer heated to, for example, 380 ° C.

What is important here is that the film-forming gas does not contain hydrogen atoms, such as a gas composed of carbon and fluorine, and the plasma does not contain hydrogen (atoms, radicals, ions, etc.). . When a CF film is formed in an environment containing hydrogen, hydrogen is contained in the film, and in a subsequent process such as annealing, it reacts with fluorine, which is a component in the film, and becomes HF gas to be removed. Therefore, the adhesion with the barrier film, which is the upper layer of the CF film, is lowered, and the strength of the CF film itself is also lowered.
Then, for example, a SiCN film 21 and a SiCOH film 22 used as a sacrificial film are stacked in this order on the surface of the CF film 20 (FIG. 1C). Subsequently, a resist mask (not shown) is formed on the SiCOH film 22, and etching is performed using, for example, plasma containing active species of halide using the resist mask and the sacrificial film described above, and via holes are formed in the CF film 20. A recess 14 is formed which includes a recess 14a corresponding to the above and a recess 14b corresponding to a wiring embedding region (trench) of the upper circuit (FIG. 1D).

  Thereafter, a conductive barrier metal film 15 such as a tantalum nitride film or a tantalum film is formed on the surface of the recess 14 (FIG. 2A), and a wiring metal 16 made of, for example, copper is embedded in the recess 14 (FIG. 2). 2 (b)), by removing the excess wiring metal 16 and the sacrificial SiCOH film 22 and the SiCN film 21 by CMP, an upper circuit layer is formed (FIG. 2C). Similarly, circuit layers are sequentially laminated on the upper layer side of the wafer W to form a semiconductor device. In addition, after the multilayer structure of the circuit layer is configured, an annealing process, for example, at 400 ° C. is performed on the multilayer structure in order to reduce dangling bonds in each film.

  Next, an embodiment of a plasma film forming apparatus used in the film forming method of the present invention and a specific example of a film forming method performed using this film forming apparatus will be described with reference to FIGS. This plasma film forming apparatus is a CVD (Chemical Vapor Deposition) apparatus that generates plasma using a radial line slot antenna. In FIG. 4, reference numeral 5 denotes, for example, a processing vessel (vacuum chamber) that is configured in a cylindrical shape. The side wall and bottom of the processing vessel 5 are made of a conductor such as aluminum-added stainless steel, and the inner wall surface is oxidized. A protective film made of aluminum is formed.

Near the center of the processing container 5, a mounting table 51, which is a mounting unit for mounting a substrate, for example, a wafer W, is provided via an insulating material 51a. The mounting table 51 is made of, for example, aluminum nitride (AlN) or aluminum oxide (Al ₂ O ₃ ), and a cooling jacket 51b through which a cooling medium flows is provided. The mounting table 51 is provided with a heater 57 as a heating means, and the heater 57 is connected to a power source 58. The mounting surface of the mounting table 51 is configured as an electrostatic chuck. Further, as described above, a bias high-frequency power source 52 having a frequency of 2 MHz or less, for example, in a range where ions can follow, is connected to the mounting table 51, for example, 800 kHz.

  The ceiling portion of the processing container 5 is open, and a planar shape, for example, is formed in a substantially circular shape so as to face the mounting table 51 through a seal member (not shown) such as an O-ring. The first gas supply unit 6 is provided. The gas supply unit 6 is made of, for example, aluminum oxide, and a gas channel 62 communicating with one end side of the gas supply hole 61 is formed on a surface facing the mounting table 51. One end side of the first gas supply path 63 is connected. On the other hand, a supply source 64 such as argon (Ar) gas or krypton (Kr) gas, which is a gas for generating plasma, is connected to the other end of the first gas supply path 63. The gas is supplied to the gas flow path 62 via the gas supply path 63, and is uniformly supplied to the space below the first gas supply unit 6 via the gas supply hole 61.

  In this example, the supply source 64, the first gas supply path 63, and the first gas supply unit 6 constitute means for supplying a plasma generating gas into the processing container 5.

  Further, the processing container 5 is a second gas supply unit having a substantially circular planar shape, for example, so as to partition between the mounting table 51 and the first gas supply unit 6. 7 is provided. The second gas supply unit 7 is made of a conductive material such as an aluminum alloy containing magnesium (Mg) or aluminum-added stainless steel, and has a number of second gas supply holes 71 on the surface facing the mounting table 51. Is formed. For example, as shown in FIG. 5, a lattice-like gas flow path 72 communicating with one end side of the second gas supply hole 71 is formed in the gas supply section 7. One end side of the second gas supply path 73 is connected. The second gas supply unit 7 is formed with a large number of openings 74 so as to penetrate the gas supply unit 7 vertically. The opening 74 is for passing the plasma and the source gas in the plasma through the space below the gas supply unit 7, and is formed, for example, between the adjacent gas flow paths 72.

  Here, for example, when the barrier film 13 is formed, the second gas supply unit 7 supplies a nitrogen gas supply source 75 and a trimethylsilane (deposition gas) via the second gas supply path 73. 3MS) gas is connected to a gas supply source 76, and the nitrogen gas and trimethylsilane gas sequentially flow into the gas flow path 72 via the second gas supply path 73, and the second gas via the gas supply hole 71. Is uniformly supplied to the space below the gas supply unit 7. In this example, the supply sources 75 and 76, the second gas supply path 73, and the second gas supply unit 7 constitute means for supplying the source gas into the processing container 5. In FIG. 2, V1, V2, and V3 are valves, and 101, 102, and 103 are flow rate adjusting means for adjusting the supply amounts of argon gas, nitrogen gas, and trimethylsilane gas into the processing vessel 5, respectively. When the above-described CF film 10 (20) is formed, a gas source in which C5F8 gas is stored is used as the supply source 76, and the second gas supply path is the same as the above-described source gas. 73 is uniformly supplied to the space below 73.

  A cover plate 53 made of a dielectric material such as aluminum oxide is provided on the upper side of the first gas supply unit 6 via a seal member (not shown) such as an O-ring. An antenna unit 8 is provided on the upper side of 53 so as to be in close contact with the cover plate 53. As shown in FIG. 6, the antenna section 8 is provided so as to close the flat antenna body 81 having a circular planar shape whose bottom surface is open, and the opening on the bottom surface side of the antenna body 81, and has a large number of slots. A disk-shaped planar antenna member (slot plate) 82 is formed, and the antenna body 81 and the planar antenna member 82 are made of a conductor to form a flat hollow circular waveguide. Yes. The lower surface of the planar antenna member 82 is connected to the cover plate 53.

Further, between the planar antenna member 82 and the antenna body 81, there is provided a slow phase plate 83 made of a low-loss dielectric material such as aluminum oxide or silicon nitride (Si ₃ N ₄ ). The retardation plate 83 is for shortening the wavelength of the microwave to shorten the guide wavelength in the circular waveguide. In this embodiment, a radial line slot antenna is formed by the antenna body 81, the planar antenna member 82, and the slow phase plate 83.

  The antenna unit 8 configured in this manner is attached to the processing container 5 via a seal member (not shown) so that the planar antenna member 82 is in close contact with the cover plate 53. The antenna unit 8 is connected to an external microwave generation means 85 through a coaxial waveguide 84, and for example, a microwave having a frequency of 2.45 GHz or 8.3 GHz is supplied. At this time, the waveguide 84A outside the coaxial waveguide 84 is connected to the antenna body 81, and the central conductor 84B is connected to the planar antenna member 82 through an opening formed in the slow phase plate 83.

  The planar antenna member 82 is made of, for example, a copper plate having a thickness of about 1 mm, and a plurality of slots 86 for generating, for example, circularly polarized waves are formed as shown in FIG. The slot 86 is formed, for example, concentrically or spirally along the circumferential direction, with a pair of slots 86a and 86b arranged in a substantially T-shape and slightly spaced apart. Since the slots 86a and 86b are arranged so as to be substantially orthogonal to each other in this way, circularly polarized waves including two orthogonal polarization components are radiated. At this time, by arranging the slot pairs 86 a and 86 b at an interval corresponding to the wavelength of the microwave compressed by the retardation plate 83, the microwave is radiated from the planar antenna member 82 as a substantially plane wave. In the present invention, the plasma generating means is constituted by the microwave generating means 85, the coaxial waveguide 84, and the antenna portion 8.

  Further, an exhaust pipe 54 is connected to the bottom of the processing container 5, and this exhaust pipe 54 is connected to a vacuum pump 56 that is a vacuum exhausting means via a pressure adjusting unit 55 that constitutes a pressure adjusting means. Can be evacuated to a predetermined pressure.

  Here, power supply to the microwave generation means 85 and the bias high-frequency power supply 52, opening / closing of the valves V1, V2, and V3 for supplying plasma gas and source gas, and flow rate adjustment means of the plasma film forming apparatus described above. 101, 102, 103, the pressure adjustment unit 55, and the like are controlled by a control unit 200 including a computer based on a program in which steps are set so that each film is formed under a predetermined condition. It has become. This program is stored in a storage medium 201 such as a flexible disk, a compact disk, a flash memory, or an MO (Magneto-Optical Disk), and is installed in the control means 200.

  Subsequently, as an example of the film forming method of the present invention performed in this apparatus, a case where the above-described barrier film 13 is formed will be described. First, through a gate valve (not shown), for example, a wafer W, which is a substrate having a lower wiring layer formed on the surface, is loaded and mounted on the mounting table 51. Subsequently, the inside of the processing vessel 5 is evacuated to a predetermined pressure, and a plasma generating gas, for example, an argon gas gas excited by microwaves is supplied to the first gas supply unit 6 via the first gas supply path 63. The flow rate is supplied at, for example, 1000 sccm. On the other hand, nitrogen gas and trimethylsilane gas, which are film formation gases, are supplied to the second gas supply unit 7 which is a film supply gas supply unit through the second gas supply path 73 at predetermined flow rates, for example, 50 sccm and 40 sccm, respectively. Supply. The inside of the processing vessel 5 is maintained at a process pressure of 17.3 Pa (130 mTorr), for example, and the surface temperature of the mounting table 51 is set to 380 ° C.

  On the other hand, when a high frequency (microwave) of 2.45 GHz and 2500 W is supplied from the microwave generating means, the microwave propagates in the coaxial waveguide 84 in the TM mode, the TE mode, or the TEM mode, and the plane of the antenna unit 8 is obtained. The microwave is covered from the slot pairs 86a and 86b while reaching the antenna member 82 and propagating radially from the central portion of the planar antenna member 82 toward the peripheral region via the inner conductor 84B of the coaxial waveguide. It is discharged toward the processing space below the gas supply unit 6 via the plate 53 and the first gas supply unit 6.

Here, since the cover plate 53 and the first gas supply unit 6 are made of a material that can transmit microwaves, for example, aluminum oxide, the cover plate 53 and the first gas supply unit 6 function as a microwave transmission window, and the microwaves transmit these efficiently. . At this time, since the slit pairs 86a and 86b are arranged as described above, circularly polarized waves are emitted uniformly over the plane of the planar antenna member 82, and the electric field density in the processing space below is made uniform. The microwave energy excites high-density and uniform plasma over the entire processing space. Then, the plasma flows into the processing space below the gas supply unit 7 through the opening 74 of the second gas supply unit 7, and the film is supplied from the gas supply unit 7 to the processing space. The active gas is activated, that is, it is turned into plasma to form active species.
This active species is transported to the surface of the wafer W, and a power of about 10 W, for example, is applied to the mounting table 51 from the high frequency power supply 52 for bias, and the active species is deposited while receiving energy from this power. A SiCN film as the barrier film 13 is formed.

  After the barrier film 13 is thus formed, the supply of the plasma generating gas and the film forming gas is stopped, and the inside of the processing container 5 is evacuated. Then, the film forming gas is switched to C5F8 gas, and the inside of the processing vessel 5 is maintained in a predetermined vacuum atmosphere while supplying the plasma generating gas and C5F8 gas into the processing vessel 5, and from the microwave generating means The CF film 20 described above is formed by supplying a high frequency of 2.45 GHz, for example, 2750 W. Thereafter, the wafer W on which the CF film 20 is formed is unloaded from the processing container 5 via a gate valve (not shown). In the above, a series of operations from loading the wafer W into the processing container 5, processing under predetermined conditions, and unloading from the processing container 5 is performed while the control unit 200 reads the program as described above. Executed.

  According to the above-described embodiment, argon gas, nitrogen gas, and trimethylsilane gas are turned into plasma, and the plasma is used to form the barrier film 13 made of the SiCN film on the lower circuit layer. High frequency power for bias is supplied. For this reason, argon ions in the plasma are attracted to the wafer W side and collide with the active species of trimethylsilane and the surface of the wafer W, resulting in the denseness of the barrier film 13 resulting from the collision. High barrier properties can be obtained. The estimation mechanism is as described above. Therefore, when the structure is annealed in a heated atmosphere of, for example, about 400 ° C. after the multilayer wiring structure is formed, the CF film 20 (FIG. 2) in which the metal, for example, copper, is an interlayer insulating film on the upper layer side. (C) (see FIG. 2) is suppressed, and conversely, fluorine that is a degassing component from the CF film 20 is prevented from diffusing into the wiring metal 11.

  Therefore, while making the barrier film 13 thinner, it is possible to suppress an increase in leakage current due to metal diffusion into the interlayer insulating film and to suppress an increase in wiring resistance due to fluorine diffusion into the wiring metal 11. This is an effective technology for future miniaturization and higher integration of semiconductor devices. In particular, the CF film, which has been attracting attention as a material for an interlayer insulating film due to its low relative dielectric constant, has a problem of degassing of fluorine during heating. Therefore, the present invention refers to the realization of an interlayer insulating film using a CF film. It is extremely effective from the viewpoint.

  The interlayer insulating film used in the semiconductor device manufactured according to the present invention is not limited to the CF film, and fluorine is added to the SiCO film, the SiCOH film, and the silicon oxide film made of silicon, oxygen, hydrogen, and carbon. An SiOF film, a silicon oxide film, or the like may be used.

  Here, regarding the magnitude of the high-frequency bias power during the formation of the barrier film 13, it is considered from the examples described later that the barrier performance of the barrier film 13 improves as the bias power increases. Since the defect was confirmed, the bias supply power value per unit area to the wafer W is 0.048 W / cm 2 (power value for the surface area of 314.16 cm 2 of the 200 mm wafer W) or less. Preferably there is.

The barrier film 13 is not limited to the SiCN film but may be a SiC film formed by using, for example, trimethylsilane gas as a film forming gas without using nitrogen gas.
Further, for example, an amorphous carbon film formed using 2-butyne gas (C ₄ H ₆ ) as a film forming gas may be used. In this case, 2-butyne gas is preferable, but 1-butyne gas, ethylene gas, acetylene gas, or the like may be used. Further, an amorphous carbon film obtained by adding a silicon-containing gas such as a silane-based gas to the hydrocarbon gas and adding silicon may be used as the barrier film. As the silane-based gas in this case, monosilane gas, disilane gas, trimethylsilane gas, or the like can be used.
Furthermore, the plasma method of gas in the present invention is not limited to using microwaves, and for example, a parallel plate type plasma generator may be used.

(Experimental example 1: Comparative test of thermal desorption gas)
A 200 mm size (8 inch size) silicon wafer was used for the experiment. First, a CF film was formed on a wafer using the plasma film forming apparatus described above, and a SiCN film having a thickness of 30 nm was further formed thereon. The conditions described above were used as the film forming conditions for these films. The bias power for forming the SiCN film was set as follows.
(Bias power)
Example 1: 30 W
Comparative Example 1: None While heating these two types of wafers, the amount of gas (HF, F) desorbed from these wafers was measured by a temperature rising gas desorption method. The result is shown in FIG. It was found that the degassing amount from the wafer gradually increased with increasing the heating temperature for both wafers. However, it was found that the degassing of HF and F was extremely reduced for the wafer of Example 1 in which the SiCN film was formed by supplying bias power. This degassing is considered to be a gas that has escaped the SiCN film from the CF film on the lower side of the SiCN film. From this, it can be seen that the barrier performance of the SiCN film against the component from the film in contact with the SiCN film is increased by supplying the bias power to form the SiCN film.

(Experimental example 2: Element penetration test in the depth direction of the wafer)
A laminate was produced in the same manner as in Experimental Example 1 above. The bias power was set as follows.
(Bias power)
Example 2-1: 5W
Example 2-2: 10W
Comparative Example 2: None These wafers were annealed in a heated atmosphere at 400 ° C. for 60 minutes, and then the fluorine and oxygen concentration profiles in the depth direction from the surface layer were examined by the SIMS method. The results shown are obtained. As can be seen from this result, the SiCN film contains fluorine and oxygen, but the contents are reduced in the order of the comparative example and Examples 2-1 and 2-2. Here, regarding the fluorine in the SiCN film, the fluorine diffused from the CF film on the lower layer side of the SiCN film during both the film forming process and the annealing process and the fluorine adhering to the inner wall of the processing container during the CF film forming process are the SiCN film. It is thought that it was scattered and mixed when forming the film. Therefore, when the SiCN film is formed or annealed, the higher the bias power, the higher the barrier property of the SiCN film against fluorine desorbed from the CF film, and the fluorine at the time of forming the SiCN film. It can be said that the amount of mixed in is reduced.
On the other hand, oxygen is considered to have scattered from the inner wall of the processing vessel 5 during the formation of the SiCN film, and as the bias power is increased, the amount of oxygen mixed in during the formation of the SiCN film decreases.
The reason why the SiCN film has a high barrier property against fluorine desorbed from the CF film is considered to be that the SiCN film becomes dense due to the impact of ions of argon gas as described above. The reason why the amount of fluorine and oxygen taken in from the atmosphere during the formation of the SiCN film is small is considered to be that these elements are scattered by the impact of argon gas ions.

(Experimental example 3: Deposition rate and refractive index)
A laminated body was produced in the same manner as in Experimental Example 1 described above, and the deposition time of the SiCN film was constant between the wafers. The bias power was set as follows.
(Bias power)
Example 3-1: 5W
Example 3-2: 10W
Comparative Example 3: None The deposition rate of the SiCN film was calculated from the thickness of the SiCN film deposited on these wafers. Further, the refractive index of the surface of this SiCN film was measured. As a result, as shown in FIG. 9, the film forming speed and the refractive index were improved as the bias power was increased. As described above, the dangling bonds are generated on the surface of the SiCN film by the impact of the ions of the argon gas, thereby increasing the probability of attachment of active species to the surface of the substrate, and as a result, the film formation rate is improved. it is conceivable that. Further, since there is a correlation in which both the refractive index and the film density increase or decrease, it can be presumed that the film density of the SiCN film has also increased due to the improvement of the refractive index.

(Experimental example 4: Appearance and adhesion)
From the above experiments, it was found that the barrier performance of the SiCN film improves as the bias power is increased. In order to confirm whether there is no problem in other characteristics even if the bias power is increased in this way, the following is performed. Tests were conducted. First, a laminate was prepared in the same manner as in Experimental Example 1 above. As a test, confirmation of the appearance of the film and confirmation of the adhesion of the SiCN film were performed. The appearance of the film was confirmed by observing the cross section of the laminate using SEM. Also, the adhesion of the SiCN film is a tape test, that is, the wafer is grooved to 5 mm square with a diamond cutter, and then the adhesive tape is applied to the entire surface of the wafer, and then the adhesive tape attached to the wafer is removed. The adhesion strength of was evaluated. In performing this evaluation, the wafer having the above-mentioned laminated structure was manufactured by changing the process conditions of the heating temperature and the bias power when forming the SiCN film as follows.
(Process conditions)
Heating temperature (° C.): 150, 200, 250, 300, 340, 380, 420 ° C.
Bias power (W): 0, 5, 10, 15, 20
The results are as shown in FIG. From this result, both the appearance and the adhesion of the SiCN film were deteriorated as the heating temperature at the time of forming the SiCN film was lowered. Further, when the bias power was 20 W or more, voids were generated in the cross section of the laminate. From these facts, it was found that the bias power when forming the SiCN film is preferably 15 W or less, that is, 0.048 W / cm 2 (power value for a surface area of 314.16 cm 2 of a 200 mm wafer). . It was also found that the heating temperature of the wafer when forming the SiCN film is preferably 340 ° C. or higher.

(Experimental example 5: Test 1 of adhesion strength between SiCN film and CF film)
A laminated body was produced in the same manner as in Experimental Example 1, and the bias power was set as follows.
(Bias power)
Example 5: 30W
Comparative Example 5: None By applying a strength test called a 4-point bending method to these wafers, a load was applied to the film thickness direction of the wafer until the interface between the SiCN film and the CF film was broken. From the size, the adhesion strength between the SiCN film and the CF film was measured (for details of the 4-point bending method, see Journal of Applied Mechanics: MARCH 1989, Vol 56 Page 77-82). Specifically, as shown in FIG. 11, after the wafer 300 having the laminated structure and another bare wafer 301 are bonded with an epoxy resin, a notch is formed on the bare wafer side to make a sample. The sample is placed on two support bars 302 arranged in parallel on the left and right sides, and the wafer is pressed by two pressing bars 303 at positions on the left and right sides of the upper surface of the sample with respect to the two bars. A load is applied to Whether or not the interface is broken is determined based on the transition of the displacement in the film thickness direction.
This test was performed seven times on each wafer, and the load at the time of breaking was averaged to obtain the results shown in FIG. From this result, it was 7.7 J / m 2 in Example 4 and 6.0 J / m 2 in Comparative Example 4. Therefore, it was found that the adhesion strength between the SiCN film and the CF film is improved by forming the SiCN film while supplying the bias power.

(Experimental example 6: Test 2 for adhesion strength between SiCN film and CF film)
From the results of Experimental Example 4 and Experimental Example 5, the region where the bias power was 15 W or less was examined in more detail. A laminate was prepared in the same manner as in Experimental Example 1, and the bias power was set as follows.
(Bias power)
Example 6: 3W, 5W, 10W, 15W
Comparative Example 6: None
For these wafers, the adhesion strength between the SiCN film and the CF film was measured by the above-described 4-point bending method. As a result, as shown in FIG. 13, the effect of applying bias power to the entire region of 3 W to 15 W (0.0095 to 0.047 W / cm 2) was obtained.

(Experimental Example 7: Test 3 for adhesion strength between SiCN film and CF film)
In a sense, the adhesion between the SiCN film as the barrier film and the CF film as the underlying insulating film is a key point in manufacturing a semiconductor device having a laminated copper wiring structure. Therefore, in order to further improve the adhesion, the present inventors have considered a method for modifying the surface of the CF film. Specifically, after the CF film is formed, a nitrogen gas or a rare gas plasma such as argon is applied to the surface while applying a bias power to the wafer to irradiate the surface of the CF film with nitrogen ions or argon ions (hereinafter referred to as “CF film”). This processing is called bias plasma processing). As a result, the CF film surface is modified, that is, the fluorine on the CF film surface is desorbed by ions and becomes carbon rich, so that the gas desorbed from the CF film during the subsequent heat treatment (during film formation or annealing). The CF film surface was moderately roughened and the adhesion effect was improved by the anchor effect.

  Further, since the film was hit by ions, a dangling bond was formed on the film surface, and a precursor for a SiCN film to be subsequently formed was bonded to this portion, so that the adhesion was further improved. Based on this idea, after the CF film is formed by the above-described method, the wafer is subjected to the bias plasma treatment with the combination shown in FIGS. 14 and 15, and then the SiCN film is formed under the condition that no bias power is applied. Lamination was performed and adhesion was evaluated by a 4-point bending method. FIG. 14 shows the result of bias plasma treatment with N2, and FIG. 15 shows the result of bias plasma treatment with Ar. In addition, the numerical value of 10 or more of the result is rounded off.

  According to this, the nitrogen plasma treatment seems to have a higher numerical value, but there is no clear superiority or inferiority, and both values exceed the value of 6.0 J / m 2 of Comparative Example 4 which is the conventional technique. Yes. In particular, in both bias plasma treatments of argon and nitrogen, a value exceeding twice the conventional value is seen, but as the value approaches 15 W, the value tends to decrease. Therefore, it can be said that the bias power value during the bias plasma treatment of the CF film is preferably 3 W to 15 W (0.0095 to 0.047 W / cm 2). In FIG. 14 and FIG. 15, there is no data relating to the application of bias power when forming the SiCN film together with the bias plasma treatment of the CF film. Even with the bias plasma treatment, a value of approximately 11.3 J / m 2 is obtained. Therefore, if the surface of the CF film is subjected to bias plasma treatment, the adhesion between the CF film and the SiCN film can be improved regardless of the subsequent method of forming the SiCN film.

  In addition, the present inventors conducted a more severe test. In this method, a CFN film is subjected to a bias plasma treatment, and then a SiCN film (without bias during film formation) is laminated, and a laminate in which a SiO2 film is further laminated thereon is produced, and this test wafer is annealed at 400 ° C. for 60 minutes. Is. Thereafter, the surface of the test wafer was observed and a tape test was performed. The surface observation was performed by counting the number of blisters (bubbles) that were traces of degassing from the CF film, and the tape test was performed by the method described above. The result is shown in FIG.

  Here, as a result of the tape test, ◯ indicates that none of the 5 mm square pieces were peeled off, △ indicates that the half of the wafer was peeled off, and xx indicates that the entire surface was peeled off. The symbol x indicates that the middle of Δ and xx is peeled off. Since this test is a harsh one that exceeds the thermal budget (thermal history) passed in the process of manufacturing an actual semiconductor device, if ○ and △ are non-defective products, the bias power value at the time of bias plasma treatment is 3 W as described above. It can be said that it is 8-12W (0.025-0.038W / cm2) more preferably among -15W. By treating the CF film surface with a bias as low as 15 W even at such a high level, the adhesion can be improved by detaching fluorine only on the very surface of the film without damaging the CF film. it can.

5 Processing Vessel 6 First Gas Supply Unit 7 Second Gas Supply Unit W Wafer 10 CF Film 20 CF Film 15 Recess 16 Barrier Metal Film 17 Copper Metal 51 Mounting Base 52 Bias High Frequency Power Supply 57 Heater 81 Antenna Body 85 Microwave Generation means

Claims (7)

In a method of forming a barrier film interposed between a wiring metal in a semiconductor device and an interlayer insulating film made of a fluorine-added carbon film,
Supplying a film-forming gas containing an organic compound and a plasma-generating gas for accelerating the formation of the film-forming gas into a processing container;
By supplying microwaves into the processing container from a planar antenna member provided on the upper part of the processing container facing the mounting part on which the substrate is mounted and having a number of slits formed in the circumferential direction Converting the plasma generating gas and the film forming gas in the processing container into plasma, and forming a barrier film containing silicon and carbon on the substrate by the plasma;
A step of applying a high-frequency power for bias to the mounting portion while this step is performed,
A film forming method, wherein the bias high frequency power supplied to the substrate per unit area is 0.047 W / cm 2 or less.   2. The film forming method according to claim 1, wherein the barrier film is a SiCN film.   3. The film forming method according to claim 1, wherein the bias high frequency power supplied to the substrate per unit area is 0.0095 W / cm 2 or more.   4. The film forming method according to claim 1, wherein the bias high frequency power supplied to the substrate per unit area is 0.025 to 0.038 W / cm <2>.   The film formation method according to claim 1, wherein the barrier film is a SiC film. The film-forming gas includes a butyne gas and a silane-based gas,
The film formation method according to claim 1, wherein the barrier film is an amorphous carbon film containing silicon.   A semiconductor device comprising a barrier film formed by the film forming method according to claim 1.

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