JP5164078B2 - Low dielectric constant insulating film - Google Patents

Description

  The present invention relates to a low dielectric constant insulating film, and more particularly to a low dielectric constant insulating film having a low dielectric constant and having both high mechanical strength and high damage resistance.

  As the integration density of semiconductor devices increases and the operation speed increases, it is required to reduce the capacitance between wires. In order to reduce the inter-wiring capacitance, a technique for reducing the dielectric constant of the interlayer insulating film is required, and research has been conducted on an insulating film called a low-k film having a relative dielectric constant of 3.0 or less.

Conventionally, low-k films have been manufactured by plasma CVD. According to the plasma CVD method, a substrate is placed on a stage in a chamber, a raw material gas containing, for example, a CH ₃ group is introduced into the chamber, this raw material gas is turned into plasma, and low-k is formed on the substrate by a polymerization reaction. A film is deposited (see, for example, Non-Patent Documents 1, 2, and 3)
However, in the case of a conventional method for producing a low-k film by plasma CVD, precursor molecules constituting the source gas are decomposed more than necessary by high-energy electrons, ultraviolet light (UV light) or photons emitted from plasma. End up. For example, the CH ₃ group is excessively detached from the Si—CH ₃ bond in the precursor molecule due to excessive energy of electrons, UV light, or photons, or the organic group is detached from the low-k film deposited on the substrate. In other words, densification proceeds. Thus, when the dissociation of gas is promoted by plasmatization, a CVD film having a desired molecular structure cannot be formed. For this reason, it has been difficult to form a film having a desired dielectric constant (k <2.2 or less) and high strength (Young's modulus ≧ 4 GPa).

  Conventionally, in order to lower the dielectric constant, many organic groups are introduced into the film to increase the number of steric obstacles, and the film density is lowered, or a hole introducing substance (porogen) is added and burned. A method has been used to introduce pores by removing them and reduce the density of the film. However, when the k value of the raw material molecules is 3.0, a porosity of about 50% is required to obtain an insulating film having a k value of 2.0 or less. Therefore, according to the technique of introducing such holes, the dielectric constant and mechanical strength are traded off.

  For example, an MPS (Molecular Pore Stacking) film has been proposed in which a low dielectric constant is achieved by forming molecular-sized pores in the film, but only k = 2.4 has been reported. . In order to lower the dielectric constant in the MPS film, in principle, it is necessary to widen the diameter of the SiO ring, but in such a case, the strength is lowered.

As a method for reducing the dielectric constant while maintaining the strength, there is a method of introducing a SiO ₂ component into the raw material molecules. However, increasing the SiO ₂ component lowers the CH ₃ concentration in the film and lowers the plasma damage resistance. In general, a film having a low dielectric constant and high strength is considered to have low plasma damage resistance.

Shin-Ichi Nakao et al. “UV / EB Cure Mechanism for Porous PECVD / SOD Low-k SiCOH Materials”, IITC, 2006 IEEE, p. 66-68 Y. Hayashi et al. “Novel Molecular-structure Design for PECVD Porous SiOCH Filmes toward 45nm-node, ASICs with k = 2.3”, IITC, 2004 IEEE, p. 225-227 N. Tajima et al. “First-principle Molecular Model of PECVD SiOCH Film for the Mechanical and Dielectric Property Investigation”, IITC, 2005 IEEE, p. 66-68

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a low dielectric constant insulating film having a low dielectric constant, high strength, and high plasma damage resistance.

In order to solve the above problems, an embodiment of the present invention is to provide a linear molecule in which a plurality of basic molecules including a SiO structure are linearly bonded, and a plurality of the linear molecules are interposed between SiO structures. A low dielectric constant insulating film made of a polymer containing Si atoms, O atoms, C atoms, and H atoms, which is bonded through a binder molecule containing of the peak signal spectrum obtained was analyzed by an outer spectroscopy, a signal indicating signal indicating the linear SiO structure found in the vicinity of a wave number of 1020 cm ^-1, the network type SiO structure found in the vicinity of wave number 1080 cm ^-1, and wavenumber when the sum of the three signals area signal indicating the cage SiO structure found in 1,120 cm ^-1 vicinity of 100%, and the area ratio of a signal indicating a linear SiO structure 49% or more, and Of the peak signal of the serial spectrum, the signal amount of the signal indicating Si (CH ₃₎ found in the vicinity of a wave number ^{7 cm -1,} Si _{(CH 3)} found in the vicinity of wavenumber of 800 cm ^-1 ₂ a signal of a signal indicating Provided is a low dielectric constant insulating film characterized in that the signal amount of a signal indicating Si (CH ₃ ) ₂ is 66% or more when the total is 100%.

  In such a low dielectric constant insulating film, the signal area ratio indicating the cage-type SiO structure can be 10 to 25%.

Further, the signal amount of the signal indicating the Si (CH ₃ ) ₂ can be 80% or more.

Further, the linear molecule is a dimer or higher methylsiloxane, and the binder molecule is one selected from the group consisting of SiO ₂ , SiO _1.5 (CH ₃ ), and SiO (CH ₃ ) _2. I can do it.

  Furthermore, when the total amount of Si atom, O atom, and C atom of the polymer containing Si atom, O atom, C atom, and H atom is 100%, the amount of C atom is 36-50%. I can do it.

  The low dielectric constant insulating film according to one embodiment of the present invention can be formed by a neutral beam CVD method using dimer or higher methylsiloxane as a source gas. In this case, dimethoxytetramethyldisiloxane can be used as the methylsiloxane of the dimer or higher.

  According to the present invention, a low dielectric constant insulating film having low dielectric constant and high strength and high plasma damage resistance is provided.

The conceptual diagram which shows the molecular structure of the low dielectric constant insulating film which concerns on one Embodiment of this invention. The chemical formula which shows the 1st example of the basic molecular structure of the polymer which comprises the low dielectric constant insulating film which concerns on one Embodiment of this invention. The chemical formula which shows the 2nd example of the basic molecular structure of the polymer which comprises the low dielectric constant insulating film which concerns on one Embodiment of this invention. The chemical formula which shows the 3rd example of the basic molecular structure of the polymer which comprises the low dielectric constant insulating film which concerns on one Embodiment of this invention. The chemical formula which shows the 4th example of the basic molecular structure of the polymer which comprises the low dielectric constant insulating film which concerns on one Embodiment of this invention. The figure which shows the neutral particle irradiation type | mold CVD apparatus for forming the low dielectric constant insulating film which concerns on one Embodiment of this invention. Chemical formula showing the molecular structure of DMOTMDS, the elimination of methyl groups, and the linear linkage of dimethylsiloxane dimers. The figure which shows the outline of the film-forming process of the low dielectric constant insulating film which concerns on one Embodiment of this invention. The spectrum figure obtained by analyzing the insulating film formed into a film by NBE-CVD in the case of substrate temperature -20 degreeC and -70 degreeC by a Fourier-transform infrared spectroscopy. The characteristic view which shows the change of SiO structure composition of the insulating film obtained by changing pulse-off time.

  Embodiments of the present invention will be described below with reference to the drawings.

  A low dielectric constant insulating film according to an embodiment of the present invention includes a linear molecule in which a plurality of basic molecules including a SiO structure are linearly bonded, and a plurality of the linear molecules are interposed between SiO 2 and SiO 2. It is formed by a polymer containing Si atoms, O atoms, C atoms, and H atoms.

  A conceptual diagram of the structure of this low dielectric constant insulating film is shown in FIG.

  In FIG. 1, a plurality of basic molecules 1 represented by rhombic figures are linearly bonded to form linear molecules 2, 3, and 4. Linear molecule 2 is a dimer in which two basic molecules 1 are bonded, linear molecule 3 is a trimer in which three basic molecules 1 are bonded, and linear molecule 4 is a basic molecule 1 It is a pentamer in which 5 are combined. These linear molecules 2, 3, and 4 are bonded through a binder molecule 5 that is represented by a cross-shaped figure therebetween. In addition, as shown in the figure, the binding by the binder molecule 5 is not limited to a straight chain but is also three-dimensionally bonded.

  2 to 5 show the basic structure of a polymer containing Si atoms, O atoms, C atoms, and H atoms that constitute the low dielectric constant insulating film according to this embodiment.

In the structure shown in FIG. 2, the basic molecule is dimethyl siloxane (SiO (CH ₃ ) ₂ ), and a dimer (tetramethyldisiloxane) in which two of the basic molecules are bonded is dimethyl silicon (Si Unit A is formed by bonding via (CH ₃ ) ₂ ), and this unit A forms a linearly connected structure. In such a polymer, the unit A has 3 Si atoms, 3 O atoms, and 6 C atoms. When the total amount of Si atoms, O atoms, and C atoms is 100%, C The amount of atoms is 50%.

In the example shown in FIG. 3, the basic molecule is dimethylsiloxane (SiO (CH ₃ ) ₂ ), and a dimer (tetramethyldisiloxane) in which two of the basic molecules are bonded is a monomethylsiloxane (SiOCH) that is a binder molecule. ₃ ) to form a unit B, which is connected via a straight chain. In such a polymer, unit B has 3 Si atoms, 3.5 O atoms, and 5 C atoms, and the total amount of Si atoms, O atoms, and C atoms is 100%. The amount of C atoms is 43%. This structure is linear, but it can be sterically linked through the O atom of monomethylsiloxane (SiOCH ₃ ), which is a binder molecule, thereby increasing the strength.

In the example shown in FIG. 4, the basic molecule is dimethylsiloxane (SiO (CH ₃ ) ₂ ), and a dimer (tetramethyldisiloxane) in which two of the basic molecules are bonded passes through the binder molecule SiO ₂ . Unit C to form a structure in which the units C are linearly connected. In such a polymer, there are 3 Si atoms, 4 O atoms, and 4 C atoms in the unit C, and when the total amount of Si atoms, O atoms, and C atoms is 100%, The amount of atoms is 36%. Although this structure is linear, it can be sterically linked through two O atoms of the SiO ₂ binder molecule, thereby increasing strength.

  The example shown in FIG. 5 has a unit structure in which the unit B shown in FIG. 3 and the unit C shown in FIG. 4 are combined.

In the basic structure shown in FIGS. 2 to 5, four dimers (tetramethyldisiloxane) in which two basic molecules composed of dimethylsiloxane (SiO (CH ₃ ) ₂ ) are bonded to two Si atoms. Of CH ₃ groups. By further linking such linear molecules, a high C concentration methylsiloxane polymer can be obtained. Linear molecules are bonded to each other by binder molecules, and assuming that one binder molecule is interposed with respect to a dimeric linear molecule, when the above-mentioned three types of binders are used, the C concentration is 36 to 50%. Thus, by introducing a large number of CH ₃ groups, low dielectric constant and high damage resistance can be obtained.

  In addition, such a methylsiloxane structure mainly composed of a linear structure is different from a low dielectric constant insulating film by introduction of pores, and a structure in which linear molecules are closely packed while being bonded with a binder having an SiO structure. Therefore, an insulating film with high strength can be obtained.

The low dielectric constant insulating film according to one embodiment of the present invention described above can be obtained by a CVD method using a neutral beam (hereinafter referred to as NBE-CVD). That is, the present inventors have earnestly studied the formation of a low dielectric constant insulating film by the NBE-CVD method, and as a result, obtained the following knowledge. That is, when a film having a siloxane bond is used as a source gas and is formed by NBE-CVD, a polymer film containing a large amount of linear components in which a SiO structure and a Si (CH ₃ ) ₃ structure are linearly bonded. It was found that this polymer film had k (dielectric constant) of 2.2 or less and E (Young's modulus) of 4 or more.

  Examples of the compound having a siloxane bond include dimethoxytetramethylsidisiloxane (DMOTMDS), dimethyldiethoxysilane (DMDEOS), and dimethyldimethoxysilane (DMDMOS). Besides these, MTMOS (methyltrimethoxysilane), trimethylsilane, cyclopentyltrimethoxysilane, bistrimethoxysilylethane, bismethyldimethoxysilylethane, bisdimethylmethoxysilylethane, bistriethoxysilylethane, etc. can also be used. It is.

  According to the NBE-CVD method, when a substrate to be deposited is placed in, for example, a DMOTMDS atmosphere, DMOTMDS molecules are adsorbed on the surface of the substrate. By selectively cutting, the above-mentioned basic molecule composed of tetramethyldisiloxane is preferentially formed, and a polymer film is obtained in which these are linearly connected via a binder having a SiO structure. In this case, it is necessary to adjust the acceleration energy so that the energy of the neutral beam on the substrate is about the binding energy of the methoxy group.

In addition, by irradiating the neutral beam in a pulsed manner (irradiation time 50 μsec / interval 200 μsec), the increase in the substrate temperature is suppressed, and the adsorption probability of the source gas molecules is increased by securing a predetermined adsorption time. A 2SiO (CH ₃ ) ₂ linear structure can be incorporated into the film more efficiently, and a low dielectric constant insulating film with k = 1.4 and E = 5 GPa is formed. In this case, an insulating film having a lower dielectric constant and a higher Young's modulus can be obtained by lowering the substrate temperature. In this way, both low dielectric constant and strength can be achieved. Note that the concentration of C in such an insulating film reaches 40%, indicating that the plasma damage resistance is high.

  The present inventors considered that the reason why the low dielectric constant, high strength, and high plasma damage resistance, which could not be achieved so far, were realized due to the molecular structure peculiar to the obtained insulating film. Structural analysis of the insulating film by external spectroscopy revealed structural requirements that satisfy low dielectric constant, high strength, and high plasma damage resistance.

A low dielectric constant insulating film was analyzed by Fourier transform infrared spectroscopy, of the peak signal of the obtained spectrum, the linear SiO structure found in the vicinity of a wave number of 1020 cm ^-1, are found in the vicinity of wave number 1080 cm ^-1 Network There are three SiO structures, a type SiO structure and a cage type SiO structure found in the vicinity of a wave number of 1120 cm- ¹ . Among these, the linear SiO structure is a linearly connected structure shown in FIG. 2, for example. In addition, the network type SiO structure is, for example, a structure sterically linked through an O atom of a linear binder shown in FIG. Further, the cage-type SiO structure is a structure in which a cage is formed by sterically connecting via two O atoms of a linear binder shown in FIG. 4, for example.

A low dielectric constant insulating film according to an embodiment of the present invention includes the above-described linear-type SiO structure, network-type SiO structure, and cage-type SiO structure, and the linear-type SiO structure forms a main structure. And That is, look at the low dielectric constant insulating film in the spectrum of the peak signal obtained were analyzed by Fourier transform infrared spectroscopy, a signal indicating a linear SiO structure found in the vicinity of a wave number of 1020 cm ^-1, near wavenumber 1080 cm ^-1 Area ratio of the signal indicating the linear SiO structure when the sum of the three signal areas of the signal indicating the network type SiO structure and the signal indicating the cage type SiO structure found near the wave number of 1120 cm ⁻¹ is 100% Needs to be 49% or more.

  As described above, the insulating film containing a large amount of the linear type SiO structure has a high strength because it has a structure in which linear molecules are closely packed while being bonded with the binder having the SiO structure. On the other hand, when the area ratio of the signal indicating the linear type SiO structure is less than 49%, since the network type SiO structure and the cage type SiO structure are included, the structure is not densely packed and the strength is low. It will be a thing.

  Note that it is difficult to obtain a desired strength only with the linear type SiO structure, and it is desirable to include a cage type SiO structure of about 10 to 25%.

Moreover, the low dielectric constant insulating film according to an embodiment of the present invention, among the peak signal of the spectrum, the signal amount of the signal indicating Si (CH ₃₎ found in the vicinity of a wave number ^{7 cm -1,} wave number 800 cm ^-1 When the total signal amount of signals indicating Si (CH ₃ ) ₂ found in the vicinity is 100%, the signal amount of signals indicating Si (CH ₃ ) ₂ needs to be 66% or more.

Thus, when the ratio of Si (CH ₃ ) ₂ is high, an insulating film having a low dielectric constant and high damage resistance can be obtained. On the other hand, when the signal amount of the signal indicating Si (CH ₃ ) ₂ is less than 66%, the CH ₃ concentration necessary for lowering the dielectric constant to a desired value cannot be obtained, and the C concentration is low. Low plasma damage resistance due to low.

  Next, an NBE-CVD method for forming a low dielectric constant insulating film according to an embodiment of the present invention will be described in detail.

  FIG. 6 shows a neutral particle irradiation type CVD (NBE-CVD) apparatus for forming a low dielectric constant insulating film according to an embodiment of the present invention. In FIG. 6, a neutral particle beam generation unit 11 is provided at, for example, an upper portion of a CVD reaction chamber (hereinafter simply referred to as a reaction chamber) 10.

  In the reaction chamber 10, a support base 13 on which a substrate 14 to be processed is placed is provided. The support base 13 includes a temperature control device (not shown), and the substrate 14 is controlled to a predetermined temperature. The reaction chamber 10 has a gas inlet 15 and an exhaust mechanism 16. The inside of the reaction chamber 10 is maintained at a predetermined pressure by the exhaust mechanism 16, and the raw material gas is guided from the gas inlet 15 onto the substrate 14 on the support base 13.

  The neutral particle beam generator 11 includes a plasma chamber 12 made of quartz, for example. A gas introduction port 17 is provided in the upper part of the plasma chamber 12, and an inert gas such as argon, helium, krypton, or the like is introduced into the plasma chamber 12 from the gas introduction port 17. A coil 18 is wound around the plasma chamber 12. One end of the coil 18 is grounded, and the other end is connected to the high frequency source 19. An anode electrode 20 as an upper electrode is provided inside and above the plasma chamber 12, and the anode electrode 20 is connected to the positive electrode of the DC power source 21 and the high-frequency source 19 through the switch SW 1. Further, a cathode electrode 22 as a lower electrode is provided at the lower part of the plasma chamber 12 and at the boundary with the reaction chamber 10. The cathode electrode 22 is connected to the negative electrode of the DC power source 21 via the switch SW2. The DC power supply 21 is a variable power supply, and the DC power supply 21 can change the electric field between the anode electrode 20 and the cathode electrode 22.

  The cathode electrode 21 needs to neutralize and pass positively charged particles and to block electrons, UV light, or photons generated from the plasma, so that the aspect ratio and the aperture ratio of the opening 22a have predetermined values. It is stipulated in.

  Furthermore, it is necessary to maintain a pressure difference between the reaction chamber 10 and the plasma chamber 12 in order to prevent the gas in the reaction chamber 10 from flowing into the plasma chamber 12. Specifically, the pressure in the reaction chamber 10 is set to 100 mmTorr or more, for example, and the pressure in the plasma chamber 12 is set to 1 Torr or more, for example. Therefore, in order to suppress the inflow of gas from the reaction chamber 10 to the plasma chamber 12, it is necessary to set the pressure difference between the plasma chamber 12 and the reaction chamber 10 to 10 times or more. In order to maintain such a pressure difference, it is preferable that the opening ratio of the opening 22a of the cathode electrode 22 is about 30%.

  The low dielectric constant insulating film is formed by the NBE-CVD apparatus shown in FIG. 6 as follows.

  First, the pressure of the plasma chamber 12 is set to 1 Torr or more, for example, and a rare gas, for example, argon gas is introduced into the plasma chamber 12. In this state, the switch SW <b> 1 is turned on, and high frequency power is supplied from the high frequency source 19 to the coil 18. For example, the high-frequency power has a frequency of 13.56 MHz, a voltage of 500 V, and a power of 1 kW. Electrons in the plasma chamber 12 are accelerated by the high-frequency electric field generated by the coil 18 and collide with the argon gas, and the gas is decomposed to generate plasma.

  In this state, when the switch SW2 is turned on, an electric field is generated between the anode electrode 20 and the cathode electrode 22, and positive charged particles in the plasma are accelerated by the electric field. The positive charged particles are neutralized by supplying electrons at the cathode electrode 22, and a neutral particle beam (NB) is generated. The neutral particle beam is guided into the reaction chamber 10 through the plurality of openings 22a. At this time, electrons, UV light, or photons generated in the plasma source are shielded by the cathode electrode 22 and do not reach the reaction chamber 10.

  The energy of neutral particles guided to the reaction chamber 10 is controlled by the acceleration voltage of ions generated in the plasma, and this acceleration voltage is varied by controlling the DC power source 21.

  In the reaction chamber 10, the substrate 14 is placed on a temperature-controlled support base 13. When, for example, DMOTMDS is introduced as a source gas from the gas inlet 15 into the reaction chamber 10, it is adsorbed on the surface of the substrate 14. Neutral particles introduced from the plasma chamber 12 collide with the DMOTMDS. The kinetic energy is converted into thermal energy by the collision of neutral particles. With the assistance of the thermal energy, dissociation of predetermined bonds of gas molecules adsorbed on the substrate is promoted, and the activated gas is sequentially deposited on the substrate 14 by causing a polymerization reaction.

FIG. 7A shows the relationship between the molecular structure of DMOTMDS and the binding energy. In the case of DMOTMDS, the bond energy of O—CH ₃ is approximately _{3 to 5} eV, and the bond energy of Si—CH ₃ is approximately 5 to 10 eV. In this embodiment, it is necessary to dissociate the O—CH ₃ bond. For this reason, it is desirable to irradiate the DMOTMDS molecules adsorbed on the surface of the substrate 14 with a neutral particle beam having an energy not less than the bond energy of O—CH ₃ and not more than the bond energy of Si—CH ₃ . That is, the DC power supply 21 is controlled to give the neutral particle beam energy of 5 eV or less and 3 eV or more to irradiate the DMOTMDS molecules. As a result, in the molecular structure shown in FIG. 7 (a), as shown in FIG. 7 (b), the bond between O and the methyl group (CH ₃ ) is dissociated to form dimethylsiloxane (SiO (CH ₃ ) ₂ ). A dimer (tetramethyldisiloxane) in which two basic molecules are bonded is obtained. As shown in FIG. 7C, the dimer is linked in a straight line, and a low dielectric constant insulating film made of a polymer containing Si atoms, O atoms, and C atoms is deposited on the substrate 14. .

In this case, in FIG.7 (c), a coupling | bonding will not arise only by a dimer, but a binder as mentioned above is needed. In NBE-CVD, in addition to the dissociation of the bond between O and the methyl group (CH ₃ ), dissociation occurs in various parts, thereby causing the above-described SiO (CH ₃ ) ₂ , SiO _1.5 (CH ₃ ), or Various binders such as SiO ₂ are formed. That is, a dimer (tetramethyldisiloxane) is linearly connected through these binders, and as described above, a low dielectric constant insulating film made of a polymer as shown in FIGS. can get.

An outline of the process for forming the low dielectric constant insulating film is shown in FIG. FIG. 8 shows a process in which DMOTMDS is adsorbed on the substrate surface, CH ₃ groups are detached by irradiation with a neutral beam, and a polymer containing linear and cage-type SiO structures is deposited.

  In the present embodiment, the neutral particle beam irradiation method is not limited to continuous irradiation, and pulsed intermittent irradiation is also possible. By intermittently irradiating, it is possible to suppress an increase in the substrate temperature during film formation, increase the adsorption efficiency of the source gas, and perform the polymerization reaction efficiently. Moreover, since the lower substrate temperature can improve the adsorption efficiency of the source gas to the substrate, it is desirable to carry out at 0 ° C. or less.

Example 1
DMDMOS and DMOTMDS were used as source gases, and two types of insulating films were deposited on the silicon substrate using a neutral particle irradiation type CVD apparatus shown in FIG. The neutral beam was continuous irradiation, the neutral beam energy was fixed at 10 eV, and the pressure in the chamber was fixed at 30 mTorr. The substrate temperature was −20 ° C. As a comparative example, an insulating film was deposited on a silicon substrate by conventional plasma CVD (PECVD) using DMOTMDS as a source gas.

The obtained three types of insulating films were analyzed by Fourier transform infrared spectroscopy. Moreover, k value was measured using the Hg probe, and Young's modulus was measured using the nanoindenter. The results are shown in Table 1 below.

As shown in Table 1 above, the insulating film formed by NBE-CVD includes a linear SiO structure of 49% or more and has Si (CH ₃ ) ₂ of 66% or more. As a result, the k value (dielectric constant) was 2.2 when DMDMOS was used as the source gas, and 1.9 when DMOTMDS was used. These values were much lower than the k value 2.6 of the insulating film formed by conventional PECVD. E (Young's modulus) was as high as 7 when DMDMOS was used as the source gas. When DMOTMDS was used, the Young's modulus was 4, which was lower than the value of an insulating film formed by conventional PECVD, but was practically usable.

Example 2
An insulating film was deposited on the silicon substrate and analyzed by Fourier transform infrared spectroscopy in the same manner as in Example 1 except that DMOTMDS was used as the source gas and the substrate temperature was lowered to −70 ° C. Moreover, k value was measured using the Hg probe, and Young's modulus was measured using the nanoindenter. The results are shown in Table 2 below. In addition, the data about the insulating film formed by conventional PECVD and the insulating film formed by NBE-CVD when the substrate temperature is −20 ° C. obtained in Example 1 are also shown.

As shown in Table 2 above, the insulating film formed by NBE-CVD with the substrate temperature lowered to −70 ° C. contains 49% or more of the linear SiO structure, and 66% or more of Si ( and a CH _{3) 2.} As a result, the k value was 1.7 and the Young's modulus was 7. These values were lower in k value and higher Young's modulus than those in the case where the substrate temperature was −20 ° C.

  Note that the insulating film formed by NBE-CVD when the substrate temperature is −20 ° C. and the insulating film formed by NBE-CVD when the substrate temperature is −70 ° C. are analyzed by Fourier transform infrared spectroscopy. The spectrum obtained in this manner is shown in FIG.

9A shows a case where the substrate temperature is −20 ° C., and FIG. 9B shows a case where the substrate temperature is −70 ° C. From FIG. 9, it can be seen that the amount of methyl groups is increased (the peak of Si (CH ₃ ) ₂ is increased) by lowering the substrate temperature to −70 ° C. This means that the adsorption probability on the substrate surface can be increased by decreasing the substrate temperature.

Example 3
An insulating film was deposited on the silicon substrate in the same procedure as in Example 2 except that the neutral beam was irradiated in a pulsed manner. The insulating film obtained by fixing the pulse-on time to 50 μs and changing the pulse-off time was analyzed by Fourier transform infrared spectroscopy, and the change in the SiO structure composition was examined. As a result, the result shown in FIG. 10 was obtained.

  FIG. 10 shows that the proportion of the linear structure increases as the pulse-off time increases. In particular, at a pulse-off time of 100 to 200 μs, a linear SiO structure of 52% or more was obtained, while the network type SiO structure decreased. As a result, the k value decreased to 1.3, and the Young's modulus exceeded 5 GPa.

  The low dielectric constant insulating film formed by the NBE-CVD method has been described above. However, the present invention is not limited to this and can be applied to a low dielectric constant insulating film formed by another method. is there.

  DESCRIPTION OF SYMBOLS 1 ... Basic molecule, 2, 3, 4 ... Linear molecule, 5 ... Binder molecule, 10 ... Reaction chamber, 11 ... Neutral particle beam generation part, 12 ... Plasma chamber, 14 ... Substrate, 19 ... High frequency power supply, 20 ... Anode electrode, 21 ... DC power supply, 22 ... Cathode electrode, 22a ... Opening.

Claims (7)

A linear molecule in which a plurality of basic molecules including a SiO structure are linearly bonded to each other, and a plurality of the linear molecules are bonded with a binder molecule including a SiO structure interposed therebetween. A low dielectric constant insulating film made of a polymer containing atoms, O atoms, C atoms, and H atoms,
Of the low dielectric constant insulating film spectral peak signal obtained and analyzed by Fourier transform infrared spectroscopy, a signal indicating a linear SiO structure found in the vicinity of a wave number of 1020 cm ^-1, are found in the vicinity of wave number 1080 cm ^-1 When the sum of the three signal areas of the signal indicating the network-type SiO structure and the signal indicating the cage-type SiO structure found near the wave number of 1120 cm ⁻¹ is 100%, the area ratio of the signal indicating the linear-type SiO structure is 49% or more,
And among the peak signals of the spectrum, the signal amount of a signal indicating Si (CH ₃ ) seen in the vicinity of a wave number of 7 cm ⁻¹ and the signal amount of a signal showing Si (CH ₃ ) ₂ seen in the vicinity of a wave number of 800 cm ^−1. A low dielectric constant insulating film characterized in that the signal amount of a signal indicating Si (CH ₃ ) ₂ is 66% or more when the sum of the above is 100%.   2. The low dielectric constant insulating film according to claim 1, wherein an area ratio of signals indicating the cage-type SiO structure is 10 to 25%. The low dielectric constant insulating film according to claim 1, wherein a signal amount of the signal indicating Si (CH ₃ ) ₂ is 80% or more. The linear molecule is a dimer or higher methylsiloxane, and the binder molecule is one selected from the group consisting of SiO ₂ , SiO _1.5 (CH ₃ ), and SiO (CH ₃ ) _2. The low dielectric constant insulating film according to any one of claims 1 to 3. When the total amount of Si atom, O atom, and C atom of the polymer containing Si atom, O atom, C atom, and H atom is 100%, the amount of C atom is 36-50%. low dielectric constant insulating film according to any one of claims 1 to 4,.   The low dielectric constant insulating film according to any one of claims 1 to 5, formed by neutral beam CVD using a dimer or higher methylsiloxane as a source gas.   The low dielectric constant insulating film according to claim 6, wherein the methylsiloxane of the dimer or higher is dimethoxytetramethyldisiloxane.

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