JP5260586B2 - Method for manufacturing insulating film for semiconductor device, method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of an insulating film for a semiconductor device capable of making an improvement in the performance of the semiconductor device and the improvement in a reliability coexist and the manufacturing method of the semiconductor device. <P>SOLUTION: When a first film 23 and a second film 24 polymerized in a vapor phase while using borazine skeleton molecules in an alkyl borazine compound dissociated by a plasma as basic units are formed as the insulating films for the semiconductor device formed on a Cu wiring 21, a carbon content in the first film 23 brought into contact with the wiring 21 is brought at a value from 9% to 35% while the effective dielectric constant of the whole first film 23 and second film 24 is brought to 4.0 or less. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing an insulating film for a semiconductor device and a method for manufacturing a semiconductor device.

  In recent years, with the development of the information and communication society, the amount of information processing has increased, and high integration and high speed of LSI (Large Scale Integrated circuit) that performs signal processing have been demanded. Miniaturization is being promoted for higher integration and higher speed of LSI, but with miniaturization, loss due to the capacitance of the insulating layer between wiring has become a problem, and the lower dielectric constant of the insulating layer has been reduced. It has become necessary. In order to increase the operation speed of the semiconductor device, it is necessary to lower the wiring dielectric resistance and the dielectric constant of the insulating film in order to reduce the capacitance between the wirings.

  In the latest semiconductor device, Cu (copper) is used for wiring in order to reduce wiring resistance. FIG. 5 shows a general structure of a semiconductor device using Cu for wiring. In the semiconductor device shown in FIG. 5, a groove is formed in the interlayer insulating film 35 by dry etching, and a Cu wiring 31 is formed in the groove by plating. In addition, when Cu diffuses into the interlayer insulating film 35, the insulating properties deteriorate. Therefore, a barrier film (insulating film) 32 and a barrier metal 36 for preventing Cu diffusion are disposed around the Cu wiring 31. Become.

  Further, in the latest semiconductor devices, in order to reduce the capacitance between wirings, not only an interlayer insulating film but also a barrier film is required to have a low dielectric constant. This is because even if the dielectric constant of only the interlayer insulating film is lowered, if the relative dielectric constant of the barrier film is high, the effective dielectric constant of the entire insulating film is increased. Therefore, as the semiconductor process rule becomes finer in the future, a barrier film having a low dielectric constant will be required. The effective dielectric constant refers to the (average) relative dielectric constant of the entire laminated film obtained from the structure of the laminated film, and the capacitance obtained from the intrinsic dielectric constant, film thickness, and area of each film constituting the laminated film. Is obtained from the combined capacity, the layer thickness and the area.

Japanese Patent No. 3778164

  Usually, Si-based materials such as SiN (silicon nitride), SiCN (silicon nitride carbide), and SiC (silicon carbide) are used for the barrier film. The relative dielectric constants of these barrier films are SiN (k = 7.0), SiCN (k = 5.0), and SiC (k = 4.0). SiCN and SiC are used. However, when SiC is used as the barrier film, there is a problem that the reliability of the semiconductor device is lowered.

  One of the causes of this problem is electromigration (EM). EM is a phenomenon in which a wiring metal moves due to an electron flow (an arrow in FIG. 5) flowing in the wiring. If the amount of movement is large, the wiring is eventually disconnected, causing a failure of the semiconductor device. The diffusion of Cu mainly occurs at the interface between Cu and the barrier film thereon, and the EM resistance tends to deteriorate as the interface diffusion of Cu becomes easier. An example of the EM failure will be described with reference to FIG. 6 corresponding to the region A in FIG. 5. Cu diffuses along the direction of electron flow at the interface between the Cu wiring 31 and the barrier film 32, and voids ( Air gap) 37 is generated, leading to disconnection.

Further, as shown in the graph of FIG. 7, the EM resistance (void growth rate) is related to the type of barrier film on Cu. For example, as shown in FIG. 8 (part corresponding to the region B in FIG. 5), in the case of a structure in which the SiC film 32 is formed as a single layer on the Cu wiring 31, due to the electron current flowing in the wiring at the interface 33 Many Cu ⁺ ions diffuse. Therefore, although the relative dielectric constant of the SiC film 32 is low, the EM resistance is poor and the reliability of the semiconductor device is lowered. As a measure for improving the EM resistance, as shown in FIG. 9 (part corresponding to the region B in FIG. 5), a structure in which the SiCN film 34 having high EM resistance is sandwiched as an intermediate layer between the Cu wiring 31 and the SiC film 32 may be considered. In this case, the diffusion of Cu at the interface 33 is suppressed and the EM resistance is improved, but the effective dielectric constant of the entire barrier film (SiC film 32 + SiCN film 34) increases.

  Thus, it has been difficult for the conventional barrier film to achieve both improvement in performance and reliability of the semiconductor device.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. By suppressing interfacial diffusion of metal wiring and increasing EM resistance, an insulating film for a semiconductor device that can simultaneously improve the performance and reliability of a semiconductor device. An object of the present invention is to provide a method for manufacturing the semiconductor device and a method for manufacturing the semiconductor device.

ここで、上記化学式１中のＲ１〜Ｒ６は、水素原子あるいは炭素数５以下のアルキル基であり、同一又は異なっていても良い。但し、Ｒ１〜Ｒ６の全てが水素原子である場合を除く。 A method for manufacturing an insulating film for a semiconductor device according to a first aspect of the present invention for solving the above-described problems is as follows.
A gas containing a raw material gas obtained by vaporizing an alkyl borazine compound represented by the following chemical formula 1 is supplied into the chamber,
Using an inductively coupled plasma generating means, an electromagnetic wave is incident into the chamber to bring the gas into a plasma state,
A substrate on which wiring of a semiconductor device is formed is disposed in the plasma diffusion region of the plasma,
When forming a layer in contact with the wiring at the time of forming a layer in contact with the wiring by performing gas phase polymerization using a borazine skeleton system molecule in the alkylborazine compound dissociated by the plasma as a basic unit, When the ratio [C / (B + N + C)] of the carbon atom C content to the sum of the boron atom B, nitrogen atom N, and carbon atom C content among the internal constituent elements is the carbon content in the film, The carbon amount of the layer in contact with the wiring is 9% or more and 35% or less, and the carbon amount of the layer is made larger than that of the other layers, and is composed of at least two layers having different carbon amounts. An effective dielectric constant of the entire film is set to 4.0 or less, and an insulating film for a semiconductor device is formed on the wiring.

Here, R1 to R6 in the chemical formula 1 are a hydrogen atom or an alkyl group having 5 or less carbon atoms, and may be the same or different. However, the case where all of R1-R6 are hydrogen atoms is excluded.

A semiconductor device according to a second invention for solving the above-mentioned problem is as follows.
In the method for manufacturing an insulating film for a semiconductor device according to any one of the first inventions,
The plasma generating means is for making electromagnetic waves enter the chamber from an antenna disposed directly above the ceiling plate of the chamber, and the substrate is positioned at a distance of 5 cm to 30 cm from the lower surface of the ceiling plate It is characterized by being arranged in.

A manufacturing method of an insulating film for a semiconductor device according to a third invention for solving the above-described problems is as follows.
In the manufacturing method of the insulating film for the semiconductor device according to any one of the first or second aspect of the invention,
The substrate is arranged in a region where an electron temperature is 3.5 eV or less.

A method for manufacturing an insulating film for a semiconductor device according to a fourth aspect of the present invention for solving the above-described problem is as follows.
In the method for manufacturing an insulating film for a semiconductor device according to any one of the first to third inventions,
The formed insulating film for a semiconductor device is treated with plasma mainly containing a gas not containing the alkyl borazine compound.

A method for manufacturing an insulating film for a semiconductor device according to a fifth aspect of the present invention for solving the above-described problem is as follows.
In the method for manufacturing an insulating film for a semiconductor device according to any one of the first to fourth inventions,
A bias is applied to the substrate.

A manufacturing method of an insulating film for a semiconductor device according to a sixth invention for solving the above-described problems is as follows.
In the method for manufacturing an insulating film for a semiconductor device according to any one of the first to fifth inventions,
The alkyl borazine compound represented by the chemical formula 1 or the chemical formula 2 is further characterized in that at least one of R 1, R 3 and R 5 is a hydrogen atom.

A manufacturing method of a semiconductor device according to a seventh invention for solving the above-described problem is as follows.
A semiconductor device insulating film is formed on a wiring of a semiconductor device using the method for manufacturing a semiconductor device insulating film according to any one of the first to sixth inventions.

  According to the present invention, two or more layers are formed as an insulating film for a semiconductor device for metal wiring of a semiconductor device, and a borazine skeleton molecule in an alkyl borazine compound dissociated by plasma is basically used as a layer in contact with the metal wiring. Using a gas-phase polymerized film (hereinafter referred to as a borazine film) as a unit, the carbon content of the film is set to 9% or more and 35% or less, and the effective dielectric of the entire insulating film for a semiconductor device. Since the rate is 4.0 or less, the interface diffusion of the metal wiring can be suppressed and the EM resistance can be increased. As a result, compared with a conventional insulating film for a semiconductor device (for example, SiC), It is possible to improve both the performance and reliability of the semiconductor device.

It is a see-through | perspective side view explaining the manufacturing apparatus used for the manufacturing method of the insulating film for semiconductor devices which concerns on this invention. (A) is a figure which shows the structural example for evaluation of the insulating film for semiconductor devices which concerns on this invention, (b) is the carbon content in the film | membrane in the insulating film for semiconductor devices shown to (a). It is a graph which shows the relationship between and interface diffusivity. (A) is a graph in which the distance from the ceiling plate to the substrate is changed and the carbon content in the film and the leakage current are measured. (B) is a graph in which the distance from the ceiling plate to the substrate is changed and the leakage current and the ratio are measured. It is the graph which measured the time-dependent change of dielectric constant. It is a schematic block diagram which shows an example of embodiment of the insulating film for semiconductor devices which concerns on this invention. It is sectional drawing which shows Cu wiring structure in the conventional semiconductor device. It is a figure explaining an example of EM failure. It is a graph which shows a barrier film and EM tolerance. It is sectional drawing which shows the structure of Cu wiring and barrier film in the conventional semiconductor device. It is sectional drawing which shows the other structure of Cu wiring and barrier film in the conventional semiconductor device.

  Hereinafter, some embodiments of a method for manufacturing an insulating film for a semiconductor device and a method for manufacturing a semiconductor device according to the present invention will be described in detail with reference to FIGS.

Example 1
FIG. 1 is a perspective side view for explaining a manufacturing apparatus used in a method for manufacturing an insulating film for a semiconductor device according to the present invention. First, the manufacturing apparatus will be described with reference to FIG. In FIG. 1, an ICP (Inductively Coupled Plasma) type plasma CVD apparatus 1 is shown as an example. However, any apparatus having an inductively coupled plasma generation mechanism may be used.

  The plasma CVD apparatus 1 used in the method for manufacturing an insulating film for a semiconductor device according to the present invention is configured such that the inside of a cylindrical vacuum chamber 2 is configured as a film forming chamber. A disk-shaped ceiling board 3 made of ceramics is disposed so as to close the opening.

  Further, for example, a high-frequency antenna 4 formed of a plurality of circular rings is disposed on the top (directly above) the ceiling plate 3, and a high-frequency power source 6 is connected to the high-frequency antenna 4 via a matching unit 5 ( Plasma generating means). The high-frequency power source 6 can feed a high oscillation frequency (for example, 13.56 MHz) to the high-frequency antenna 4 than the low-frequency power source 13 described later, and the electromagnetic waves that generate plasma in the vacuum chamber 2 are transmitted to the ceiling plate 3. Can enter through the light. This is a configuration of a so-called ICP type plasma generation mechanism. A plasma state having a high electron density can be generated by an ICP type plasma generation mechanism.

  Further, a support base 7 is provided at the lower part of the vacuum chamber 2 so that, for example, a substrate 8 such as a semiconductor is electrostatically attracted and held on the upper surface of the support base 7 using an electrostatic chuck or the like. It has become. The support table 7 can be moved up and down by an elevating device 9 so that the distance between the plasma generated in the vacuum chamber 2 and the substrate 8 during film formation can be adjusted. Yes.

  The support 7 is provided with an electrode portion 11, and a low frequency power source 13 is connected to the electrode portion 11 via a matching unit 12. The low frequency power supply 13 can apply a bias to the substrate 8 by applying an oscillation frequency (for example, 4 MHz) lower than that of the high frequency power supply 6 to the electrode portion 11. Further, the support base 7 is provided with a temperature control device such as a heater and a refrigerant flow path for controlling the temperature of the substrate 8, and the temperature control device (not shown) is used to bring the substrate 8 to a desired temperature (for example, 150). ˜700 ° C.).

  The substrate 8 is configured to be transferred onto the support base 7 by opening the gate door 17 provided on the side wall of the vacuum chamber 2, and after placing on the support base 7, the gate door 17 is closed, The process described later is performed inside the vacuum chamber 2.

  A plurality of gas nozzles 14 are provided on the side wall portion of the vacuum chamber 2 at a position lower than the ceiling plate 3 and higher than the support base 7, and are controlled from the gas nozzle 14 by controlling the gas control device 15. A gas having a desired flow rate can be supplied inside. As the gas to be supplied, an alkyl borazine compound represented by the following chemical formula 3 and a carrier gas are used.

ここで、上記化学式３中の側鎖基Ｒ１〜Ｒ６は、水素原子あるいは炭素数５以下のアルキル基であり、同一又は異なっていても良い。但し、Ｒ１〜Ｒ６の全てが水素原子である場合を除く。中でも、Ｒ１、Ｒ３、Ｒ５の少なくとも１つが水素原子であるアルキルボラジン化合物が好ましい。

Here, the side chain groups R1 to R6 in the chemical formula 3 are hydrogen atoms or alkyl groups having 5 or less carbon atoms, and may be the same or different. However, the case where all of R1-R6 are hydrogen atoms is excluded. Among these, alkylborazine compounds in which at least one of R1, R3, and R5 is a hydrogen atom are preferable.

  The alkyl borazine compound is vaporized and then supplied to the vacuum chamber 2 using an inert gas as a carrier gas. As the carrier gas, a rare gas such as helium or argon or nitrogen is generally used. However, a mixed gas thereof or a mixed gas to which hydrogen, oxygen, ammonia, methane, or the like is added as necessary. Also good. The alkyl borazine compound is preferably a liquid at normal temperature and pressure, but may be a solid as long as it can be vaporized (sublimated) by heating or the like.

  Further, the vacuum chamber 2 is provided with a pressure control device (vacuum pump, pressure control valve, vacuum gauge, etc .; not shown), and the inside of the vacuum chamber 2 is exhausted from the bottom side using the vacuum pump, The inside of the vacuum chamber 2 is adjusted to a desired pressure using a vacuum gauge and a pressure control valve.

  The high-frequency power supply 6, the lifting device 9, the low-frequency power supply 13, the gas control device 15, the temperature control device, the pressure control device, and the like are integrally controlled by the main control device 16, and a desired process set in advance. It is controlled according to the process and process conditions.

  Here, FIG. 2A shows a structural example for evaluating the insulating film for a semiconductor device according to the present invention. 2A corresponds to, for example, the region B in the semiconductor device shown in FIG. 5. Here, only the wiring in the semiconductor device and the insulating film portion for the semiconductor device are illustrated, and other configurations are omitted. ing.

  In this configuration example, a Cu wiring 21 is used as a wiring of a semiconductor device, and a borazine film 22 is formed on the Cu wiring 21 as a barrier film (insulating film for a semiconductor device) using a manufacturing method described later. ing. As will be described in detail later, this borazine film 22 is a gas phase polymerized based on a borazine skeleton molecule in the alkylborazine compound represented by the above chemical formula 3 dissociated by plasma as a basic unit. The dielectric constant can be lowered. If the interdiffusion of Cu can be suppressed in the borazine film 22 having a low relative dielectric constant, that is, if the interfacial diffusivity of Cu can be made smaller than SiC, the EM resistance can be improved, and as a result, the performance of the semiconductor device is improved. And improved reliability.

  Then, in order to evaluate the interfacial diffusivity of Cu, the samples 1 to 5 for evaluation having the structure shown in FIG. 2A were prepared by changing the carbon content of the borazine film. As a comparative sample, a sample having a SiC / Cu structure (see FIG. 8 described above) similar to the structure shown in FIG. Sample 4 and sample 5 have the same carbon content in the film, but have different dielectric constant conditions. Specifically, the relative permittivity is changed by adjusting RF power and LF power (bias power), which are process conditions described later. However, the carbon amount also changes with that alone, so that the same carbon amount is obtained. The distance from the ceiling plate 3 to the substrate 8 and the supply amount of ammonia, an amine compound containing an alkyl group having 1 to 3 carbon atoms, and the like are adjusted.

  The amount of carbon in the borazine film is obtained by analyzing the element content in the thin film by, for example, X-ray photoelectron spectroscopy (XPS). Carbon (C), boron (B) and The ratio (%) of the content of carbon (C) to the sum of the elemental contents of nitrogen (N), that is, C / (C + B + N) is obtained.

  The interfacial diffusion rate of Cu is measured by using a stress relaxation rate measurement method. This stress relaxation measurement method is based on the fact that since stress relaxation involves the movement of atoms, the amount correlated with the interfacial diffusion of Cu induced by EM can be measured by measuring the stress relaxation rate of Cu. As a result, the EM resistance can be estimated. For example, a slow stress relaxation rate means that the interfacial diffusivity is small, and in this case, it means that the EM resistance is improved. Conversely, a fast stress relaxation rate means that the interfacial diffusivity is large. Yes, which means that the EM resistance is reduced.

  Table 1 below shows the measurement results of the carbon content in the film and the interfacial diffusivity of Cu in the comparative sample and the evaluation samples 1 to 5. Moreover, FIG.2 (b) is a graph which shows the relationship between the carbon amount in a film | membrane, and the interfacial diffusion rate of Cu in the evaluation samples 1-5. In the graphs of Table 1 and FIG. 2B, the Cu interface diffusivity in the comparative sample (SiC / Cu structure) is normalized as 1. Table 1 also shows measured values of the relative dielectric constant of each sample, and also shows evaluation results of reliability and responsiveness as a semiconductor device. The reliability is evaluated by EM resistance estimated from the interface diffusivity, and the responsiveness is evaluated by dielectric constant.

  As can be seen from the graphs in Table 1 and FIG. 2 (b), the sample 1 having a carbon content of 7% in the borazine film has higher interfacial diffusivity and lower EM resistance than the comparative sample. Become. Also, the dielectric constant is high, and as a result, the reliability as a semiconductor device is deteriorated and the responsiveness is also lowered. On the other hand, samples 2 to 5 whose carbon content in the borazine film is 9%, 10%, and 35% have low interface diffusivities of 0.9, 0.4, and 0.1 compared to the comparative samples, The EM resistance is improved, and as a result, the reliability of the semiconductor device is improved.

Thus, there is a correlation between the amount of carbon in the borazine film and the interfacial diffusion rate of Cu. If the amount of carbon in the borazine film is 9% or more, the EM resistance is improved as compared with the SiC / Cu structure. Will do. However, the amount of carbon in the film correlates with the leakage current of the film, and if the amount of carbon in the film is too large, the leakage current increases. Therefore, the leakage current applicable as an insulating film is 5E-8 A / cm ² or less. It is necessary to. For this purpose, the inventors know that the amount of carbon in the film needs to be 35% or less. Therefore, the carbon content in the borazine film may be in the range of 9% to 35%.

  In each of Samples 2 to 5, the relative permittivity is 3.7, 3.4, 3.4, or 2.5 lower than the relative permittivity of SiC of 4.0 due to the process conditions described later.

  Here, the distance from the ceiling plate 3 to the substrate 8 as one of the conditions for controlling the carbon content in the film, the relative dielectric constant, and the leakage current will be described with reference to FIG. 3A is a graph in which the amount of carbon in the borazine film and the leakage current are measured by changing the distance from the ceiling plate 3 to the substrate 8, and FIG. It is the graph which changed the time-dependent change of the leakage current of a borazine film | membrane, and a dielectric constant, changing the distance to the board | substrate 8. FIG.

  As described above, the plasma CVD apparatus 1 has an ICP type plasma generation mechanism, and can form plasma regardless of the position of the support base 7 (substrate 8). In the film formation chamber of the plasma CVD apparatus 1, the plasma (plasma generation region) is formed so as to have a center (maximum value) of electron density at a position slightly away from the ceiling plate 3. Gradually decreases monotonically as the distance from the substrate 8 toward the substrate 8 on the support 7 increases. As the plasma generation region approaches the direction of the substrate 8, the electron density of the plasma becomes two-thirds or less of the maximum electron density of the plasma generation region, and the electrons are not accelerated and are diffused only by the concentration gradient. A plasma diffusion region is generated.

  Further, in the plasma CVD apparatus 1, as described above, the support base 7 can be moved up and down by the lift apparatus 9, and the distance from the ceiling plate 3 to the support base 7 (substrate 8) can be changed. By using the lifting device 9 to dispose the support base 7 (substrate 8) at a position further away from the ceiling plate 3, the substrate 8 is disposed in a region where the electron density is low, that is, a plasma diffusion region, Thereby, a region having a low electron density of several centimeters to several tens of centimeters can be secured above the substrate 8.

When the distance from the ceiling plate 3 to the substrate 8 was changed and measured, the results shown in FIG. 3A were obtained for the carbon content in the borazine film and the leakage current. At this time, as the source gas, alkylborazine (R1, R2, R5 = C ₂ H ₅ , R2, R4, R6 = CH ₃ ) is 50 sccm, Ar is 200 sccm, RF power is 4200 W / m ² , and pressure is A borazine film was formed at 30 mTorr and a substrate temperature of 320 ° C.

  As shown in FIG. 3A, it can be seen that the amount of carbon in the borazine film decreases as the distance from the ceiling plate 3 to the substrate 8 increases. And the leakage current is also reduced so as to be proportional to the carbon content in the film.

  Further, in order to determine an appropriate range for the distance from the ceiling plate 3 to the substrate 8, when the leakage current of the borazine film and the change in relative dielectric constant with time are measured by changing the distance from the ceiling plate 3 to the substrate 8, FIG. The result as shown in 3 (b) was obtained. As shown in FIG. 3B, the lower limit of the distance from the ceiling plate 3 to the substrate 8 is 5 cm, and when approaching the ceiling plate 3 from this position, as shown in FIG. In addition, the dissociated alkyl group is taken into the film as it is, and the amount of carbon in the film increases, so that the leakage current also increases.

  On the other hand, the upper limit of the distance from the ceiling plate 3 to the substrate 8 is 30 cm. When the distance from the ceiling plate 3 is longer than this position, the reactive species of the borazine skeleton are deactivated, and the gas phase polymerization proceeds. This results in an incomplete borazine skeleton structure film that is likely to deteriorate over time, so that the change in relative permittivity with time increases. This change in relative permittivity with time is a difference between the relative permittivity after thin film formation and after 2 weeks. From this, it can be seen that the distance from the ceiling plate 3 to the substrate 8 is preferably in the range of 5 cm or more and 30 cm or less. Note that, when the distance from the ceiling plate 3 to the substrate 8 is increased, the film formation rate is decreased, and thus film formation cannot be performed in a practical time.

  Further, from the viewpoint of the electron temperature, when the arrangement position of the substrate 8 is examined, it is desirable to form the film by arranging the substrate 8 at a position where the electron temperature is 3.5 eV or less. This electron temperature is an electron temperature at which a neutral molecule in which an alkyl group dissociated from an alkylborazine compound is recombined does not dissociate again, and is the lowest dissociation energy necessary for the neutral molecule to dissociate. The threshold was defined from 5 eV.

  Based on the above, next, the configuration of the insulating film for a semiconductor device of this example will be described in detail with reference to FIG. FIG. 4 is a schematic view showing an example of an insulating film for a semiconductor device according to the present invention, and corresponds to, for example, a region B in the semiconductor device shown in FIG. In FIG. 4 as well, only the wiring in the semiconductor device and the insulating film portion for the semiconductor device are shown, and other configurations are omitted. Also, the same components as those shown in FIG. 2A are denoted by the same reference numerals, and redundant description is omitted.

  In the samples 4 and 5 described above (see Table 1), the carbon content of the borazine film is 35% and the interfacial diffusivity is 0.1, but the relative permittivity is different, and the relative permittivity of the sample 4 is different. Is 3.4, whereas the relative dielectric constant of Sample 5 is as low as 2.5. In Sample 5, although the relative permittivity changes with time due to moisture absorption, the film stability is slightly inferior to Samples 2 to 4, although it is within the allowable range.

  Therefore, in order to improve the film stability while ensuring the EM resistance, as shown in FIG. 4, the barrier film (insulating film for semiconductor device) has a multilayer structure (here, a two-layer structure), and the wiring 21 A first film 23 made of a borazine film having a high carbon content in the film (low interfacial diffusivity) and a low relative dielectric constant is formed thereon, and the film stability is high on the first film 23. A second film 24 made of a film such as SiC, SiCN, or a borazine film having a high relative dielectric constant is formed.

  In the multilayer structure, since the Cu wiring 21 is in contact with the first film 23 made of a borazine film, Cu interfacial diffusion is suppressed and EM resistance can be ensured. If only the first film 23 is used, the film stability is slightly inferior. However, by forming the second film 24 having high film stability on the first film 23, moisture absorption by the first film 23 is prevented. It can suppress and improve membrane stability. At this time, the relative dielectric constant and the film thickness of the first film 23 and the second film 24 are set so that the effective dielectric constant of the first film 23 and the second film 24 is less than 4.0. It is set.

  For example, in Table 2 below (see Sample 6), as an example, a borazine film having a relative dielectric constant of 2.5 and a film thickness of 10 nm is formed as the first film 23, and the second film 24 is formed as the second film 24. A borazine film having a relative dielectric constant of 3.6 and a film thickness of 40 nm is formed, and the effective dielectric constant of the first film 23 and the second film 24 is set to 3.3. It should be noted that a film having a relative dielectric constant of 3.6 increases the amount of LF applied in the film formation process compared with a film having a relative dielectric constant of 2.5 in order to increase film stability.

  And when the sample 6 of the said conditions was produced and the performance was evaluated, the carbon content in the film | membrane of the 1st film | membrane 23 which contact | connects the Cu wiring 21 will be 35%, and the interface diffusivity will be set to 0.1. Compared with the sample, the interface diffusivity is low, and the EM resistance is improved. As a result, the reliability of the semiconductor device is improved. Further, the effective dielectric constant is a relative dielectric constant 3.3 lower than that of SiC, which improves not only the EM resistance but also the responsiveness as a semiconductor device. As a result, in the conventional semiconductor device, It is possible to achieve both improvement in performance and reliability of the semiconductor device which has been difficult.

  In addition, since the second film 24 having high film stability is provided on the upper layer of the first film 23, moisture absorption by the first film 23 is suppressed, and a change with time in relative permittivity (+0) in the sample 5 is suppressed. .05), the change with time of the relative dielectric constant of Sample 6 was +0.02, and the film stability could be improved. A borazine film has a tendency to decrease in film stability when the relative dielectric constant decreases. However, by using the above structure, the film stability can be ensured even when a borazine film having a low relative dielectric constant is used. Is possible.

  As described above, when the insulating film for a semiconductor device is formed by using both the first film 23 and the second film 24 as a borazine film, the first film 23 is composed of layers having different carbon contents in the film and is in contact with the wiring 21. The amount of carbon in the film 23 is larger than that in the second film 24. The same applies to the case of a multilayer structure composed of borazine films having three or more layers.

  Next, a method for manufacturing a borazine film formed on the wiring of the semiconductor device will be described with reference to the plasma CVD apparatus 1 shown in FIG. This is applied to the formation of the first film 23 made of a borazine film. When the second film 24 is also a borazine film, the relative permittivity, the carbon content in the film, etc. are different. The present invention can also be applied to the formation of the film 24.

(Preliminary steps)
Before the first film 23 (borazine film) is formed on the Cu wiring 21, a device portion such as a transistor is formed on a semiconductor substrate 8 such as Si (silicon), and the wiring is connected to the device portion. Then, a Cu wiring 21 is formed.

(Step 1)
After the Cu wiring 21 is formed, the substrate 8 is transferred from the gate door 17 into the vacuum chamber 2 by using a transfer device (not shown), placed on the support base 7, and held by suction with an electrostatic chuck. The support 7 is controlled by a temperature controller to any temperature of 150 ° C. to 700 ° C., which is a temperature range in which the alkyl borazine compound does not liquefy and the borazine skeleton molecules start to condense, By controlling the temperature of the support base 7, the temperature of the substrate 8 can be processed at a desired set temperature. The height of the support base 7 (substrate 8) is moved by the lifting device 9 to any position within the range of 5 to 30 cm from the ceiling plate 3.

  By using a lifting device 9, the distance from the ceiling plate 3 to the substrate 8 (the surface of the support base 7) is increased, so that the distance from the plasma generation region having a high plasma density is increased, and electrons from the plasma generation region are separated. The substrate 8 is disposed in a plasma diffusion region where the amount of diffusion decreases. Accordingly, during film formation, the alkyl group dissociated from the alkylborazine compound by plasma can be neutralized before being transported to the surface of the substrate 8. The neutralized alkyl group has a low probability of recombination with the borazine skeleton molecule and is exhausted as it is. As a result, when the borazine skeleton molecules are vapor-phase polymerized, the incorporation of alkyl groups into the first film 23 is reduced, and the vapor-polymerized borazine skeleton molecules are increased in molecular weight. It can be a good film.

  When the carbon content of the first film 23 is controlled within the range of 9% or more and 35% or less as described above, the distance from the ceiling plate 3 to the substrate 8 is set to reduce the carbon content in the film. What is necessary is just to make the distance from the ceiling board 3 to the board | substrate 8 close | similar.

(Step 2)
The gas control device 15 is used to supply a carrier gas (for example, He gas) from the gas nozzle 14 into the vacuum chamber 2, and the degree of vacuum in the vacuum chamber 2 is controlled to about 10 to 50 mTorr by the vacuum control device. An RF power having a frequency of 13.56 MHz is supplied from the high frequency power source 6 to the high frequency antenna 4 via the device 5, and electromagnetic waves are incident on the vacuum chamber 2 to generate plasma in the vacuum chamber 2. The RF power supplied by the high-frequency power source 6 is within a power range in which the plasma is stably ignited until the series of processes is completed, and the side chain group of the borazine skeleton molecule can be dissociated without breaking the borazine skeleton structure. It is controlled by one of power of a ^{800W / m 2 ~53000W / m 2} . The flow rate of the carrier gas supplied from the gas nozzle 14 is controlled to an appropriate flow rate until a series of processes is completed, but is preferably about 200 sccm to 1000 sccm.

  If the carbon content of the first film 23 is controlled within the range of 9% or more and 35% or less as described above, if the carbon content in the film is to be reduced, the RF power should be reduced within the above range. In order to increase the frequency, the RF power may be increased within the above range. Further, since the relative permittivity of the borazine film tends to increase as the RF power increases, the RF power may be reduced within the above range in order to obtain a low relative permittivity.

(Step 3)
After stabilization of the plasma, an LF power having a frequency of 4 MHz is supplied to the electrode 11 from the low frequency power supply 13 through the matching unit 12, and the alkylborazine compound shown in Chemical Formula 3 evaporated from the gas nozzle 14 in the vacuum chamber 2 is supplied. Supplying while gradually increasing to a predetermined amount, the degree of vacuum in the vacuum chamber 2 is controlled to about 10 to 50 mTorr. At this time, LF power low-frequency power source 13 to power (bias power), in the film forming process is controlled by one of power in the range of ^{0W / m 2 ~14500W / m 2} . When LF power is applied, gas phase polymerization between borazine skeleton-based molecules is promoted, so that not only the mechanical strength is improved but also water resistance, heat resistance, and chemical resistance are improved. However, the leakage current tends to increase as the LF power increases, and the upper limit of the LF power is 14500 W / m ² because the leakage current is 5E-8 A / cm ² or less that is applicable as an insulating film. Become.

  When the carbon content of the first film 23 is controlled within the range of 9% or more and 35% or less, the bias applied to the substrate 8 is within the above range when the carbon content in the film is to be reduced. If it is desired to increase the bias, the bias applied to the substrate 8 may be reduced within the above range. Further, since the relative permittivity of the borazine film tends to increase as the bias increases, in order to obtain a low relative permittivity, the bias applied to the substrate 8 may be reduced within the above range. .

Along with the alkylborazine compound, at least one selected from the group consisting of ammonia and an amine compound containing an alkyl group having 1 to 3 carbon atoms (for example, C ₂ H ₅ NH ₂ ) may be supplied. Supply to the extent. As described above, it is desirable that the alkyl group dissociated from the alkylborazine compound is not taken into the first film 23 to be formed from the viewpoint of reducing the leakage current. By using at least one selected from the group consisting of amine compounds containing an alkyl group, the alkyl group is neutralized more efficiently and is not taken into the first film 23 to be formed. Can do. For example, there is ethylamine (C ₂ H ₅ NH ₂ ) as an amine compound having 2 carbon atoms, but when a dissociated alkyl group and a dissociated ethylamine are reacted, an alkylamine which is a neutral molecule is obtained. Is unlikely to recombine with a borazine skeleton molecule, so it will be exhausted as it is.

  Further, supply of ammonia, an amine compound containing an alkyl group having 1 to 3 carbon atoms, etc., in addition to reducing the incorporation of the alkyl group into the first film 23, during the cross-linking of the borazine skeleton structures. A structure (B—N—B bond) in which nitrogen dissociated from ammonia, an amine compound containing an alkyl group having 1 to 3 carbon atoms, or the like is formed as a spacer is formed, and borazine skeleton structures are difficult to condense. There is also an effect. However, when the addition amount of ammonia, an amine compound having 1 to 3 carbon atoms, or the like is larger than the flow rate of the alkyl borazine compound, the film formation rate decreases, so the amine compound addition ratio (amine compound flow rate / alkyl borazine compound) The molar ratio of the flow rate is preferably 30 times or less.

  When the carbon content of the first film 23 is controlled within the range of 9% or more and 35% or less as described above, ammonia or an alkyl group having 1 to 3 carbon atoms can be used to reduce the carbon content in the film. The supply amount of the amine compound or the like containing suffices to be increased, and when it is desired to increase, the supply amount of the amine compound or the like containing ammonia or an alkyl group having 1 to 3 carbon atoms may be reduced.

  The film forming reaction in the film forming process is performed under the above process conditions. Specifically, the borazine skeleton system molecule (borazine ring) and the side chain group in the alkyl borazine compound are dissociated by plasma, and the borazine skeleton system molecules in the plasma state are vapor-phase polymerized to form the support base 7. By adsorbing on the Cu wiring 21 of the substrate 8 placed thereon, the first film 23 having a desired carbon content and a desired relative dielectric constant is formed.

  When the film forming process is performed for a predetermined time and the first film 23 having a desired film thickness (for example, about 10 nm) is formed on the substrate 8, the film forming process is completed, and then the reaction promoting process is performed. To be implemented. In the case where the second film 24 is a borazine film, the LF application amount during the film formation process is changed as compared with the first film 23 in order to improve the film stability by changing the process conditions. When the second film 24 is formed after the first film 23 by increasing the film, and the second film 24 is formed, the film forming process is completed, and then the reaction promoting process is performed. Will be.

(Step 4)
In the reaction promoting step, specifically, the LF power from the low-frequency power source 13 that feeds the electrode 11 is made larger than the LF power in the film forming step, and the alkylborazine compound that is supplied from the gas nozzle 14 into the vacuum chamber 2; Ammonia, an amine compound containing an alkyl group having 1 to 3 carbon atoms, and the like are gradually reduced, and noble gas (He, Ar, etc.) or N _{2 that} does not react with the first film 23 and the second film 24 itself. The vacuum degree in the vacuum chamber 2 is controlled to about 10 to 50 mTorr. In this reaction promotion step, [LF power × application time] by the low-frequency power source 13 is controlled by electric power at which the LF power is not less than 254500 W / m ² · sec and the LF power is not more than 127400 W / m ² . This is a condition for accelerating the crosslinking reaction between borazine skeleton molecules but not causing damage to the thin film. The above process conditions promote the reaction in the reaction promoting step, that is, the crosslinking reaction between borazine skeleton-based molecules.

  In this reaction promoting step, the reactive active groups remaining in the first film 23 and the second film 24 formed in the film forming step are condensed to accelerate the crosslinking reaction and remove the B—H bond. ing. Therefore, by promoting the crosslinking reaction, the lowering of the dielectric constant is further promoted, and the change with time is suppressed by the removal of the B—H bond serving as the active site of the reaction with moisture, thereby improving the stability. Further, by promoting the crosslinking reaction, higher mechanical strength can be achieved (mechanical strength Young's modulus of 10 GPa or more). As a result, chemical resistance, workability, and CMP (Chemical Mechanical Polish) resistance are improved. It will be. In addition, heat resistance can also be achieved because an inorganic polymer material superior in heat resistance compared to an organic polymer material is used.

By implementing the above procedure, in addition to realizing a borazine film having low interfacial diffusivity, low dielectric constant, low leakage current, and high mechanical strength characteristics, the change with time of these characteristics is small. A borazine film can be realized. For example, as its specific characteristics, low dielectric constant (relative dielectric constant 3.5 or less), low leakage current (leakage current 5E-8A / cm ² or less), and high mechanical strength (Young's modulus 10 GPa or more) are realized. In addition, as the stability of the characteristics, it is possible to realize the stability of the relative permittivity (change in the relative permittivity with time of 0.1 or less). This change in relative permittivity with time is a difference between the relative permittivity after thin film formation and after 2 weeks.

  On the other hand, when the second film 24 formed on the first film 23 is a film having high film stability, for example, SiC or SiCN, after the completion of the reaction promoting step for the first film 23, the film SiC, SiCN, or the like to be the second film 24 is formed so that the overall effective dielectric constant is less than 4.0. Also in this case, as in the case where both the first film 23 and the second film 24 are borazine films, the EM resistance can be improved, the reliability of the semiconductor device can be improved, and the response as the semiconductor device can be improved. As a result, it is possible to improve both the performance and reliability of the semiconductor device, which has been difficult with the conventional semiconductor device. In addition, since the second film 24 having high film stability is provided in the upper layer of the first film 23, moisture absorption in the first film 23 can be suppressed and film stability can be improved.

  In this embodiment, copper is used as an example of the wiring used in the semiconductor device. However, the present invention is not limited to copper wiring, and may be applied to wiring made of an aluminum-based material.

  The present invention is suitable as a barrier film for copper wiring of a semiconductor device.

DESCRIPTION OF SYMBOLS 1 Plasma CVD apparatus 2 Vacuum chamber 3 Ceiling board 4 High frequency antenna 5 Matching device 6 High frequency power supply 7 Support stand 8 Substrate 9 Lifting device 11 Electrode 12 Matching device 13 Low frequency power supply 14 Gas nozzle 15 Gas control device 16 Main control device 17 Gate door 21 Cu Wiring 22 Borazine film 23 First film 24 Second film

Claims (7)

A gas containing a raw material gas obtained by vaporizing an alkyl borazine compound represented by the following chemical formula 1 is supplied into the chamber,
Using an inductively coupled plasma generating means, an electromagnetic wave is incident into the chamber to bring the gas into a plasma state,
A substrate on which wiring of a semiconductor device is formed is disposed in the plasma diffusion region of the plasma,
When forming a layer in contact with the wiring at the time of forming a layer in contact with the wiring by performing gas phase polymerization using a borazine skeleton system molecule in the alkylborazine compound dissociated by the plasma as a basic unit, When the ratio [C / (B + N + C)] of the carbon atom C content to the sum of the boron atom B, nitrogen atom N, and carbon atom C content among the internal constituent elements is the carbon content in the film, The carbon amount of the layer in contact with the wiring is 9% or more and 35% or less, and the carbon amount of the layer is made larger than that of the other layers, and is composed of at least two layers having different carbon amounts. A method of manufacturing an insulating film for a semiconductor device, wherein an effective dielectric constant of the entire film is set to 4.0 or less and an insulating film for a semiconductor device is formed on the wiring.

Here, R1 to R6 in the chemical formula 1 are a hydrogen atom or an alkyl group having 5 or less carbon atoms, and may be the same or different. However, the case where all of R1-R6 are hydrogen atoms is excluded. In the manufacturing method of the insulating film for semiconductor devices of Claim 1 ,
The plasma generating means is for making electromagnetic waves enter the chamber from an antenna disposed directly above the ceiling plate of the chamber, and the substrate is positioned at a distance of 5 cm to 30 cm from the lower surface of the ceiling plate A method for manufacturing an insulating film for a semiconductor device, comprising: In the manufacturing method of the insulating film for semiconductor devices of Claim 1 or Claim 2 ,
A method of manufacturing an insulating film for a semiconductor manufacturing apparatus, wherein the substrate is disposed in a region where an electron temperature is 3.5 eV or less. In the manufacturing method of the insulating film for semiconductor devices as described in any one of Claims 1-3 ,
A method of manufacturing an insulating film for a semiconductor device, comprising: processing the deposited insulating film for a semiconductor device with a plasma mainly composed of a gas not containing the alkylborazine compound. In the manufacturing method of the insulating film for semiconductor devices as described in any one of Claims 1-4 ,
A method of manufacturing an insulating film for a semiconductor device, wherein a bias is applied to the substrate. In the manufacturing method of the insulating film for semiconductor devices as described in any one of Claims 1-5 ,
The method for producing an insulating film for a semiconductor device, wherein the alkylborazine compound represented by the chemical formula 1 or the chemical formula 2 further has at least one of R1, R3, and R5 as a hydrogen atom. By using the manufacturing method of the insulating film for the semiconductor device according to claim 1, claim 6, a method of manufacturing a semiconductor device, which comprises forming a semiconductor device insulating film on the wiring of a semiconductor device.

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