JP4250209B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device having an insulating film for electrically separating conductive regions between wirings, particularly an insulating film containing F (fluorine).
[0002]
[Prior art]
Conventionally, as an insulating film (interlayer insulating film) for electrically separating the wiring of elements, a thermally oxidized SiO 2 is used.₂A film or SiO formed by a CVD method under reduced pressure or normal pressure using a gas such as silane or tetraethoxysilane (TEOS) as a source gas₂A membrane is mainly used.
[0003]
Especially for insulation between aluminum (Al) wiring, TEOS and O as source gases₂And O_ThreeSiO by plasma CVD using mixed gas with₂The film is used because it can be formed at a low temperature of about 400 ° C.
[0004]
By the way, in recent years, the problem of signal transmission delay has become more prominent with the increase in integration and speed of semiconductor elements. The cause is that the time interval of signal transmission increases due to the synergistic effect of increasing the wiring resistance (R) due to the reduction of the wiring cross-sectional area and increasing the wiring resistance (R) due to the reduction in the wiring interval as the element is miniaturized. (RC delay).
[0005]
The RC delay hinders the high-speed operation of the semiconductor device, and is a main factor that hinders the performance improvement of the logic device and the high-speed SRAM. As countermeasures, it is possible to reduce the wiring resistance by using Cu and Ag having a lower specific resistance than Al as a wiring material, and to reduce the dielectric constant of the insulating film interposed between the wirings and to reduce the capacitance between the wirings. Two points are important.
[0006]
SiO formed by conventional plasma CVD method₂The relative dielectric constant of the film is 4.0 to 5.0, and thermal oxidation SiO₂It has been found that it also shows a large value for that of the membrane (3.9). Then, about reduction of a dielectric constant, it is SiO.₂It has been studied to introduce F into the film, and it has been reported that the introduction of F actually reduces the dielectric constant.
[0007]
F introduction methods include F ion implantation, SiF (OC₂H_Five)_ThreeAnd H₂CVD method using O and H₂SiF₆An aqueous solution of boric acid is added to a supersaturated aqueous solution of₂FEOS and O₂And a gas containing F (CF_Four, NF_ThreeEtc.) is known.
[0008]
SiO₂Regarding the state of F in the film, formation of Si-F bonds has been confirmed by infrared absorption spectrum measurement. F₂Molecule or FO_xSome are incorporated as numerators (x = 2, 3).
[0009]
With the introduction of F, SiO₂It has also been found that the density of the film decreases, and due to the synergistic effect of this decrease in density and the decrease in electronic and ionic polarizabilities due to the formation of Si-F bonds, SiO 2₂The relative dielectric constant of the film is reduced.
[0010]
However, this kind of F added SiO₂Film (F-added SiO₂The film had the following problems.
[0011]
That is, F-added SiO₂The film absorbs moisture by being left in the atmosphere, and this moisture absorption causes generation of new Si—OH and desorption of F, thereby causing a problem that the relative permittivity increases again and high-speed operation cannot be achieved. . Moreover, F-added SiO₂The hygroscopicity of the film increases with increasing F concentration.
[0012]
The desorbed F is F-added SiO.₂Diffusion to the wiring arranged in the upper layer and lower layer of the film causes the corrosion and adhesion deterioration of the wiring, resulting in a problem that the reliability is lowered.
[0013]
[Problems to be solved by the invention]
As described above, F-doped SiO is used as an insulating film having a low relative dielectric constant.₂Although a film has been proposed, desorption of F occurs due to hygroscopicity, which causes problems such as a rise in relative permittivity and corrosion of wiring.
[0014]
The present invention has been made in consideration of the above circumstances, and the object of the present invention is to prevent wiring corrosion and adhesion deterioration due to moisture absorption, including Si, O, F, SiO₂Another object of the present invention is to provide a method of manufacturing a semiconductor device including a step of forming an insulating film having a network structure.
[0015]
[Means for Solving the Problems]
    [Overview]
  The gist of the present invention is SiO₂Surrounding SiO centered on Si with F in the film₂Network structure (local SiO₂Focusing on the network structure), this local SiO₂In the network structure, an F-added insulating film is formed under film forming conditions in which the number of F bonded to Si does not become 2 or more.
  That is, in order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention (Claim 1) electrically isolates conductive regions, contains Si, O, F, and SiO.₂When forming an insulating film having a network structure ofThe activation energy required for replacing the element bonded to Si with F is larger when F is bonded to Si than when F is not bonded to Si.As source gas, SiF (OCH₂ CF_Three)_Three, SiF (OCH₂C (OR)_Three)_Three(R is a functional group), SiF (OCH₂CF₂R)_Three(R is a functional group), SiF (OCH₂C (OR)₂R ′)_Three(R and R 'are functional groups), SiF (OCH₂C (NR₂)_Three)_Three(R is a functional group), SiF (OCH₂C (NR₂)₂R ′)_Three(R and R 'are functional groups), SiF (OCH₂CRO)_Three(R is a functional group), SiF (OCH₂CN)_Three ,SiF (OCH₂NO₂)_Three, SiF (OCH₂COOR)_Three(R is a functional group) or SiF_n(OCH₂CF₂R)_4-n(N = 1-3, R is a functional group)And the difference between the two activation energies is ΔE _a [Kcal / mol] (> 0), film formation temperature T [K], Boltzmann constant k _B ΔE _a / (K _B ・ T) ≧ 1.5 × 10 ^-3 Under conditions that satisfy, The insulating filmplasmaIt is formed by CVD method
[0016]
According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device (Claim 2), wherein the two activation energies are ΔE in the method for manufacturing a semiconductor device (Claim 1)._a[Kcal / mol] (> 0), film formation temperature T [K], Boltzmann constant k_BΔE_a/ (K_B・ T) ≧ 1.5 × 10^-3It satisfies the following conditions.
[0019]
Further, the following can be given as an invention that can obtain the same effect as the semiconductor device manufacturing method (claims 1 to 4) according to the present invention.
[0020]
That is, the conductive regions are electrically separated and contain Si, O, F, SiO₂When the insulating film having the network structure is formed by the CVD method, the activation energy necessary for replacing the element bonded to Si with F as the film material is F bonded to the Si. In the case, the predetermined value (= ΔE) is obtained, compared with the case where F is not bonded to Si._aThe activation energy required to replace the element bonded to Si with F by [kcal / mol]) is larger when Si and O with F substitution are bonded to Si. The predetermined value (= δE) than the case where Si and O in which F substitution does not occur is bonded to Si._aWhen a substance larger by [kcal / mol] is used, (ΔE_a+ ΔE_a) / (K_B・ T) ≧ 1.5 × 10^-3And ΔE_a≧ δE_aThe insulating film is formed under film forming conditions that satisfy the conditions.
[0021]
In the above invention, between the conductive regions means between the diffusion layer on the substrate surface and the wiring or the electrode, between the wiring, between the electrodes, between the wiring and the electrode, or from other layers of conductive members. Between the two areas.
[0022]
The membrane material refers to a source gas, a precursor generated from the source gas, and a reaction intermediate generated from the source gas.
[0023]
Desirable embodiments of the invention are as follows.
[0025]
(2) When the present invention is applied to an interlayer insulating film, SiO to which F according to the present invention is added is used as the interlayer insulating film.₂Film and this SiO₂An insulating film having a lower hygroscopicity than the film (for example, pure SiO containing no F)₂A laminated film is used.
[0030]
[Action]
According to the study by the present inventors, if the film forming conditions of the present invention are satisfied, SiO₂F-doped SiO with network structure₂In the film, even if the F concentration is increased, SiO having Si combined with two or more F that causes hygroscopic deterioration.₂It was found that the occurrence of the network structure can be effectively suppressed. Therefore, according to the present invention, the F-added SiO having a lower dielectric constant than that of the conventional one without causing corrosion or adhesion deterioration due to hygroscopicity.₂A film can be formed.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
(Experiment / Discussion)
First, the experiment and the considerations that led to the creation of the present invention will be described. The present inventors have made SiO containing no F.₂3D mesh SiO₂SiF formed by F replacing O when F is sequentially introduced randomly into_nO_{(4-n) / 2}The F concentration dependence of the statistical distribution (n = 1, 2, 3, 4) was examined using the Monte Carlo method.
[0032]
1 and 2 show the SiF obtained by the above method._nO_{(4-n) / 2}The statistical distribution of (n = 1, 2, 3, 4) is shown.
[0033]
FIG. 1 shows the activation energy E under a certain film formation temperature T._aFIG. 2 shows the activation distribution E on the contrary._aShows a statistical distribution when the film formation temperature T is changed under a certain condition.
[0034]
The reaction probability P when F is inserted into the bond between Si and the adjacent Si atom is the activation energy E of F insertion._aIt was assumed that the film formation temperature T was determined by the number n of F already bonded to Si.
[0035]
Activation energy E_aIs E in the case where F is not bonded at all (n = 0) in proportion to the number n (n ≧ 1) of F already bonded to Si.⁰ _aThan ΔE_aIt gets bigger and E_a= E_a ⁰+ NΔE_aIt becomes.
[0036]
At this time, the reaction probability P is
P = α (4-n) / 4 × exp (−E_a/ K_BT)
= Α (4-n) / 4xexp (-E_a ⁰/ K_BT) xexp (-nΔE_a/ K_BT)
α: Proportional coefficient
E_a ⁰: Si- (O)_FourActivation energy [kcal / mol] of F ← → O substitution reaction at Si-O bond
ΔE_a: Difference in activation energy [kcal / mol]
k_B  : Boltzmann constant = 1.9872 × 10^-3[Kcal / mol]
T: Deposition temperature [K]
It becomes.
[0037]
Deposition temperature T is fixed at 400 ° C. and ΔE_aSiF while changing_nO_{(4-n) / 2}From the results of FIG. 1 in which the F concentration dependence of the statistical distribution of (n = 1, 2, 3, 4) was examined, the rise of the concentration distribution of n ≧ 2, that is, Si that is a structure that deteriorates the moisture absorption resistance is obtained. Local SiO with multiple F bonds₂The critical F concentration at which the formation of the network structure becomes remarkable is ΔE_aWhen it is> 1.0 kcal / mol, it shifts remarkably to the high concentration side.₂It can be seen that the formation of the network structure is suppressed to 5% or less of the structure in which only one F is bonded.
[0038]
Activation energy difference ΔE_aIs fixed at 1.5 kcal / mol, and while changing the film formation temperature T, SiF_nO_{(4-n) / 2}From the results of FIG. 2 in which the F concentration dependency of the statistical distribution of (n = 1, 2, 3, 4) was examined, the rise of the concentration distribution of n ≧ 2, that is, Si that is a structure that deteriorates the moisture absorption resistance is obtained. Local SiO with multiple F bonds₂The critical concentration at which the formation of the network structure becomes prominent is significantly shifted to the high concentration side when T ≦ 400 ° C., and in particular, local SiO in which a plurality of F is bonded to Si at an F concentration of 10 at% or less.₂It can be seen that the formation of the network structure is suppressed to 5% or less of the structure in which only one F is bonded.
[0039]
Based on the above results, a wider range of ΔE_a, T_a/ K_BT ≧ 1.5 × 10^-3Satisfying activation energy difference ΔE_aBy using a raw material gas, a precursor generated from the raw material gas or a reaction intermediate, and when the raw material gas is fixed, by using a CVD method in which the film formation temperature T is set to a predetermined level, It has been found that the formation of Si in which two or more Fs having a structure with a severe hydrolysis reaction are bonded can be suppressed even at a higher F concentration than before. In addition, the ab initio molecular orbital calculation reveals that a larger amount of activation energy is required when Si that undergoes a substitution reaction of F is linked to adjacent Si and O that have already undergone F substitution. It was.
[0040]
This activation energy increment is expressed as δE_aAs mentioned above, the activation energy E_aE_a= E⁰ _a+ NΔE_a+ ΧδE_a(Χ: χ = 1 when F is bonded to adjacent Si, χ = 0 when F is not bonded to adjacent Si)_nO_{(4-n) / 2}(N = 1, 2, 3, 4) and F_lSiOSiF_mThe statistical distribution of (a structure in which F is simultaneously present in adjacent Si) was examined by the Monte Carlo method.
[0041]
The results are shown in FIGS. In the figure, the Y axis is 10^Three/ T [K] is shown, and the range is 1.25 to 2.25. In the figure, parameters 10, 15, and 20 indicate the F concentration [at%].
[0042]
  From these figures, δE_aAs (> 0) increases, a structure in which F is simultaneously present in adjacent Si becomes difficult to form rapidly. In particular, ΔE_aIs δE_aIf smaller, SiF is heavily hydrolyzed.₂The structure is easier to form. To suppress this, (ΔE_a+ ΔE_a) /k _BT ≧ 1.5 × 10^-3And ΔE_a≧ δE_aΔE that satisfies_aAnd δE_aBy using a precursor gas or a reaction intermediate generated from the precursor gas, or using a CVD method in which the film-forming temperature T is set, two or more Fs having a structure with a severe hydrolysis reaction are bonded. It can be seen that the formation of Si can be suppressed even at a higher F concentration than in the past.
[0043]
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0044]
(First embodiment)
FIG. 3 is a schematic diagram showing a schematic configuration of a plasma CVD apparatus used for forming an interlayer insulating film according to the first embodiment of the present invention. In this embodiment, SiF (OCH as a source gas₂CF_Three)_ThreeAnd O₂And a mixed gas of TEOS are used.
[0045]
Next, a method for forming a multilayer wiring using the plasma CVD apparatus will be described. First, a semiconductor substrate 11 such as a silicon substrate on which elements are formed is set on a substrate support 12. Next, the semiconductor substrate 11 is heated by a resistance heater 13 provided in the substrate support 12 and set to a predetermined substrate temperature (film formation temperature).
[0046]
A cooling pipe 14 for circulating a coolant is provided in the substrate support 12 so that the substrate temperature (film formation temperature) can be prevented from exceeding a predetermined temperature.
[0047]
The substrate temperature (film formation temperature) is determined by SiOD in the thermal desorption spectroscopy (TDS) measurement performed in advance.₂It is set to 400 ° C. or higher (for example, 470 ° C.) at which dehydration condensation of the structural water (Si—OH, H—OH) taken in is remarkable.
[0048]
As a result, SiO₂Achievement of densification of network and SiO due to structural water residue₂Suppression of formation of free volume (void) required for network relaxation and Si-F elongation is realized.
[0050]
Next, the source gas, TEOS, is 50 cm in the film formation chamber (reaction vessel) 16.^Three/ Min, O₂500cm^Three/ Min, SiF (OCH₂CF_Three)_Three0-1500cm^Three/ Min, SiH_Four50cm^ThreeAt the same time, the pressure in the film forming chamber 16 is maintained at 133 Pa by the exhaust device 10. The flow rate is adjusted by the gate valve 18.
[0051]
Next, 1 kW of RF power of 13.56 MHz is applied to an electrode (counter electrode) 17 facing the semiconductor substrate 11 by a high frequency power source 19 to start discharging, and at the same time, the substrate is driven by a high frequency power source 15 provided on the substrate support 12. By applying 500 W RF bias at 350 kHz to the support 12, SiO added with F as an interlayer insulating film₂Film (F-added SiO₂Film) is formed.
[0052]
At this time, it has energy that can give the surface of the interlayer insulating film being formed with energy of about 12 eV or more, which is energy required for breaking the O—H bond of Si—OH and H—OH that can be taken into the interlayer insulating film. Electrons or ions (typically F^±, O^±, O₂ ^±By irradiating the surface of the interlayer insulating film being formed with ions), the decomposition of Si—OH on the film surface is promoted and SiO₂Refine the network. In addition, non-bridging oxygen that can be generated during film formation is due to network densification by irradiation with oxygen ions and SiH._FourDecomposition product SiH_nIt is removed by termination according to (n = 1 to 3).
[0053]
In this way, as shown in FIG. 4A, SiO having a thickness of 500 nm added on the semiconductor substrate 11 is SiO.₂Film (F-added SiO₂Film) 20 is formed.
[0054]
Next, as shown in FIG. 5A, F-doped SiO2 is obtained by DC magnetron sputtering.₂After forming an Al film on the film 20, the Al film is patterned to form a first Al wiring 21 having a wiring width of 500 nm and a wiring thickness of 400 nm.
[0055]
Next, as shown in FIG.₂800 nm thick F-doped SiO with the same film formation method as film 20₂After forming the film 22, an Al film having a thickness of 400 nm is formed in the same manner as the Al wiring 21, and this Al film is patterned to form a second-layer Al wiring 23.
[0056]
Finally, as shown in FIG.₂800 nm thick F-doped SiO with the same film formation method as film 20₂A film 24 is formed.
[0057]
F-added SiO₂The formation of Si—F bonds in the film 24 was confirmed by infrared absorption spectrum measurement. That is, the infrared absorption spectrum has about 1080 cm.^-1, About 800cm^-1, About 450cm^-1And SiO₂In addition to the absorption peak attributed to the inherent normal vibration mode, it is approximately 935 cm.^-An absorption peak attributed to the Si-F bond was observed. This F-added SiO₂The refractive index of the film was 1.36, and the relative dielectric constant was 2.8.
[0058]
  In the case of the embodiment, F-added SiO with high F concentration₂Although a film was formed, it was approximately 980 cm, which was attributed to a structure in which two F atoms were bonded to Si.^-1Unlike the conventional case, the absorption band intensity of was lower than the detection limit.Therefore, SiO having a structure in which the existence ratio of two or more F atoms bonded to Si atoms is sufficiently smaller than the existence ratio of one bonded Si atom. ₂ Is realized.
[0059]
In the present embodiment, as the plasma CVD apparatus, a CVD apparatus is used in which discharge in the film formation chamber is performed by applying a high frequency to the electrode facing the semiconductor substrate. However, another CVD apparatus is used. Also good.
[0060]
For example, a conventionally used parallel plate type plasma CVD apparatus, microwave discharge, magnetron discharge, etc. 1 × 10¹¹Ion / cm^ThreeCVD apparatus capable of forming the above high density plasma, for example, plasma CVD apparatus using cyclotron resonance, plasma CVD apparatus using induced current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate Even if a CVD apparatus or the like is used, by controlling the conditions during the formation of the insulating film, the same F-added SiO as in this embodiment₂A film can be formed.
[0061]
FIG. 5A and FIG. 5B are respectively F-doped SiO films formed by the method of the present embodiment (the present invention).₂In order to investigate the hygroscopicity of the film, it is the result of measuring the change in the infrared absorption spectrum immediately after deposition and after being left in the atmosphere for one week.
[0062]
In the figure, the horizontal axis corresponds to the concentration of added F (Si-F / Si-O ratio), about 935 cm.^-1Si-F stretching peak integrated intensity of about 1080 cm^-1SiO₂It is a value normalized by the inverse symmetric stretching peak integrated intensity. The vertical axis represents SiO₂Corresponding to the absorption amount ((Si—OH, H—OH) / SiO ratio) which is the concentration of the structural water taken in, about 3750 to 3000 cm^-1Si-OH, H-OH peak integrated intensity of about 1080 cm^-1SiO₂It is a value normalized by the inverse symmetric stretching peak integrated intensity.
[0063]
From FIG. 5, it can be seen that the structural water decreases immediately after deposition, and the amount of moisture absorption after leaving in the atmosphere decreases. In addition, when F density | concentration is low (less than 2%), it seems that the amount of moisture absorption is increasing because there are considerably many OH groups in a film | membrane.
[0064]
Furthermore, it was found by FT-IR that the formation of a structure in which two or more Fs are attached to one Si is suppressed because the symmetry of the Si—F bond in the film is not greatly changed.
[0065]
As described above, according to the present embodiment, even if the F concentration is increased in order to lower the dielectric constant, the F-added SiO does not cause deterioration in hygroscopicity.₂A film can be formed. Therefore, by reducing the inter-wiring capacitance, signal delay can be suppressed, and a high-speed operation semiconductor device can be realized without causing a decrease in reliability due to hygroscopic deterioration.
[0066]
(Second Embodiment)
FIG. 6 is a process cross-sectional view illustrating a multilayer wiring forming method according to the second embodiment of the present invention. In order to improve the hygroscopicity, SiO added F is used as an interlayer insulating film.₂Film (F-added SiO₂Film) and SiO with no F added₂Film (pure SiO₂This is an example using a laminated insulating film.
[0067]
First, as shown in FIG. 6A, a boron phosphorous glass (BPSG) film 32 having a thickness of 800 nm is formed on a semiconductor substrate 31 such as a silicon substrate on which elements are formed. Next, after forming an Al film having a thickness of 400 nm by sputtering, the Al film is patterned to form a first Al wiring 33.
[0068]
Next, as shown in FIG. 6 (b), TEOS and O as source gases.₂100 nm thick pure SiO 2 by plasma CVD using a mixed gas with₂After forming the film 34, as in the first embodiment, TEOS and O2 are used as source gases.₂And SiH_FourAnd SiF (OCH₂CF_Three)_ThreeF-doped SiO with a thickness of 500 nm by plasma CVD using a mixed gas with₂A film 35 is formed.
[0069]
Next, as shown in FIG. 2B, TEOS and O as source gases.₂100 nm thick pure SiO 2 by plasma CVD using a mixed gas with₂The film 36 is made of F-added SiO.₂Formed on the film 35.
[0070]
Next, as shown in FIG. 6C, a resist (not shown) is applied to the entire surface, exposed and developed to form a resist pattern, and then the Al wiring 33 is formed by dry etching using the resist pattern as a mask. Via holes 37 are opened in the upper insulating films 34, 35 and 36.
[0071]
Next, as shown in FIG.₆And SiH_FourThe tungsten film 38 is embedded in the via hole 37 by combining the selective CVD method or the non-selective CVD method using the mixed gas with chemical mechanical polishing or resist etch back.
[0072]
Next, as shown in FIG. 6D, an Al film having a thickness of 400 nm is formed by sputtering, and this Al film is patterned to form a second layer of Al wiring 39, and then pure SiO 2 having a thickness of 100 nm is formed.₂Film 40, 500 nm thick F-doped SiO₂Film 41, 100 nm thick pure SiO₂The film 42 is formed sequentially.
[0073]
Pure SiO₂The film is F-doped SiO₂Less hygroscopic than membranes. Therefore, according to the present embodiment, moisture absorption of the interlayer insulating film can be further suppressed as compared with the first embodiment, and a decrease in reliability typified by an increase in dielectric constant and wiring corrosion can be effectively prevented. . Pure SiO₂Instead of a film, SiO in which the F concentration in the film is low and does not exhibit hygroscopicity₂The same effect was obtained even when using.
[0074]
Further, instead of the BPSG film 32, F-added SiO₂The film 35 may be used to insulate the diffusion layer formed on the substrate surface from the wiring formed on the substrate.
[0075]
(Third embodiment)
FIG. 7 is a schematic diagram showing a schematic configuration of a plasma CVD apparatus used for forming an interlayer insulating film according to the third embodiment of the present invention. In this embodiment, SiF (OCH as a source gas₂CF_Three)_Three, O₂, SiH_Four, NF_ThreeAnd a mixed gas of TEOS are used.
[0076]
In the figure, reference numeral 50 denotes a film forming chamber (reaction vessel) made of an insulating material. Inside the film forming chamber 50, a substrate support for placing a semiconductor substrate 51 such as a silicon substrate on which elements are formed. A stand 52 is provided. Further, a nozzle 56 for introducing a source gas is provided above the film forming chamber 50. In addition, an exhaust device 55 is provided below the film forming chamber 50, so that the inside of the film forming chamber 50 can be evacuated.
[0077]
The substrate support 52 is provided with a resistance heater 53 which is an internal heater and a cooling pipe 54 for circulating the coolant. A high frequency power source 59 is connected to the substrate support base 52. A high frequency coil 57 is wound around the side wall of the film forming chamber 50, and a high frequency power source 58 is connected to the high frequency coil 57.
[0078]
Next, a method for forming a multilayer wiring using the plasma CVD apparatus for forming an interlayer insulating film will be described. This is an example in which the present invention is applied to an N-added insulating film.
[0079]
First, the semiconductor substrate 51 on which the element is formed is set on the substrate support base 52, and is set to a predetermined substrate temperature (film formation temperature) by the resistance heater 54.
[0080]
The substrate temperature is determined by SiOD in the thermal desorption spectrum (TDS) measurement performed in advance.₂Is set to 400 ° C. or higher (for example, 470 ° C.) at which dehydration condensation of the structural water (Si—OH, HOH) taken in is remarkable.
[0081]
As a result, SiO₂Achievement of densification of network and SiO due to structural water residue₂Suppression of formation of free volume (void) required for network relaxation and Si-F elongation is realized.
[0083]
Next, 50 cm of TEOS is used as a source gas in the deposition chamber 50.^Three/ Min, O₂500cm^Three/ Min, SiH_Four50cm^Three/ Min, NF_Three500cm^Three/ Min, SiF (OCH₂CF_Three)_Three0-1500cm^ThreeAt the same time, the pressure in the film forming chamber 50 is kept at 133 Pa.
[0084]
Next, 13.56 MHz RF power is applied to the high frequency coil 57 on the side wall of the film forming chamber 50 by the high frequency power source 58 to start discharging, and at the same time, an RF bias of 350 kHz is applied to the substrate support base 52 by the high frequency power source 59. Then, an interlayer insulating film is formed.
[0085]
At this time, energy that can be applied to the surface of the interlayer insulating film being formed is about 12 to 25 eV or more of energy required for breaking the O—H bond of Si—OH and H—OH that can be taken into the interlayer insulating film. Electrons or ions with (typically F^±, O₂ ^±By irradiating the surface of the interlayer insulating film being formed with ions), the decomposition of Si—OH on the film surface is promoted and SiO₂Refine the network.
[0086]
In addition, non-bridging oxygen that can be generated during film formation includes network densification by oxygen ion irradiation,_FourDecomposition product SiH_n(N = 1 to 3).
[0087]
Thus, as shown in FIG. 8A, SiO having a thickness of 500 nm added with F and N on the semiconductor substrate 51.₂Film (SiO with F, N added₂Film) 70 is formed.
[0088]
Next, as shown in FIG. 8B, after an Al film is formed by DC magnetron sputtering, this Al film is patterned to form a first Al wiring 71 having a wiring width of 500 nm and a wiring thickness of 400 nm. To do.
[0089]
Next, as shown in FIG.₂F and N-added SiO with a thickness of 800 nm by the same film formation method as the film 70₂A film 72 is formed. Next, similarly to the Al wiring 71, an Al film of 400 nm is formed, and this Al film is patterned to form a second-layer Al wiring 73.
[0090]
Finally, as shown in FIG.₂F and N-added SiO with a thickness of 800 nm by the same film formation method as the film 70₂A film 74 is formed.
[0091]
  N-added SiO₂Although the film has a high dielectric constant, the dielectric constant can be lowered by adding F as in this embodiment. At this time, as in the case of the other embodiments, even if the F concentration is increased, problems such as hygroscopic deterioration do not occur.Therefore, SiO having a structure in which the existence ratio of two or more F atoms bonded to Si atoms is sufficiently smaller than the existence ratio of one bonded Si atom. ₂ Is realized.
[0092]
In the present embodiment, as the plasma CVD apparatus, a CVD apparatus is used in which discharge in the film forming chamber is performed by applying high-frequency power to an electrode provided on the side wall of the film forming chamber. It may be used.
[0093]
For example, a conventionally used parallel plate type plasma CVD apparatus, microwave discharge, magnetron discharge, etc. 1 × 10¹¹Ion / cm^ThreeCVD apparatus capable of forming the above high density plasma, for example, plasma CVD apparatus using cyclotron resonance, plasma CVD apparatus using induced current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate Even if a CVD apparatus or the like is used, N and F-added SiO, which are the same as those in the present embodiment, are controlled by controlling the conditions during the formation of the insulating film.₂A film can be formed.
[0094]
(Fourth embodiment)
FIG. 9 is a process cross-sectional view illustrating a multilayer wiring forming method according to the fourth embodiment of the present invention. In this embodiment, SiF (OCH as a source gas₂CF_Three)_Three, O₂, SiH_Four, BF_ThreeAnd a mixed gas with TEOS is used. Further, the same plasma CVD apparatus as that of the third embodiment is used as an interlayer insulating film forming apparatus.
[0095]
First, as in the third embodiment, the semiconductor substrate 51 on which elements are formed is set on the substrate support base 52 and set to a predetermined heating temperature (film formation temperature) by the resistance heater 54.
[0096]
The heating temperature is determined by SiOD in the thermal desorption spectroscopy (TDS) measurement performed in advance.₂Is set to 400 ° C. or higher (for example, 470 ° C.) at which dehydration condensation of the structural water (Si—OH, HOH) taken in is remarkable.
[0097]
As a result, SiO₂Achievement of densification of network and SiO due to structural water residue₂Suppression of the shape of the free volume (void) required for network relaxation and Si-F elongation is realized.
[0099]
  Next, 50 cm of TEOS is used as a source gas in the deposition chamber 50.^Three/ Min, O₂500cm^Three/ Min, SiH_Four, BF_Three500cm^Three/ Min,SiF (OCH ₂ CF _Three ) _Three  0-1500cm^ThreeAre introduced simultaneously at a flow rate of / min so that the pressure in the film forming chamber 50 is maintained at 133 Pa.
[0100]
Next, 13.56 MHz RF power is applied to the high frequency coil 57 on the side wall of the film forming chamber 50 by the high frequency power source 58 to start discharging, and at the same time, an RF bias of 350 kHz is applied to the substrate support base 43 by the high frequency power source 59. Then, an interlayer insulating film is formed.
[0101]
At this time, energy that can give the surface of the interlayer insulating film being formed with energy of about 12 to 25 eV or more, which is energy required for breaking the O—H bond of Si—OH and H—OH that can be taken into the interlayer insulating film. Electrons or ions with (typically F^±, O₂ ^±By irradiating the surface of the interlayer insulating film being formed with ions), the decomposition of Si—OH on the film surface is promoted and SiO₂Refine the network.
[0102]
Furthermore, SiO having a structure in which the proportion of Si atoms in which two or more F atoms are bonded is sufficiently smaller than the proportion of Si atoms in which one F atom is bonded.₂Was confirmed by FT-IR. The ratio is preferably at most 1/3. In this way, as shown in FIG. 9A, SiO having a thickness of 500 nm in which F and B are added onto the semiconductor substrate 51.₂Film (SiO with F and B)₂Film) 80 is formed.
[0103]
Next, as shown in FIG. 9B, after an Al film is formed by DC magnetron sputtering, this Al film is patterned to form a first Al wiring 81 having a wiring width of 500 nm and a wiring thickness of 400 nm. Form.
[0104]
Next, as shown in FIG.₂F and B doped SiO with a thickness of 800 nm by the same film formation method as the film 80₂A film 82 is formed. Next, an Al film having a thickness of 400 nm is formed in the same manner as the Al wiring 81, and then the Al film is patterned to form a second-layer Al wiring 83.
[0105]
Finally, as shown in FIG. 5C, F and B added SiO₂F and B doped SiO with a thickness of 800 nm by the same film formation method as the film 82₂A film 84 is formed.
[0106]
In the present embodiment, as the plasma CVD apparatus, a CVD apparatus is used in which discharge in the film forming chamber is performed by applying high-frequency power to an electrode provided on the side wall of the film forming chamber. It may be used.
[0107]
For example, a conventionally used parallel plate type plasma CVD apparatus, microwave discharge, magnetron discharge, etc. 1 × 10¹¹Ion / cm^ThreeCVD apparatus capable of forming the above high-density plasma, for example, plasma CVD apparatus using cyclotron resonance, plasma CVD apparatus using induced current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate Even if a CVD apparatus or the like is used, by controlling the conditions at the time of forming the insulating film, SiO and B and F similar to those of the present embodiment are added.₂A film can be formed.
[0108]
In addition, this invention is not limited to embodiment mentioned above.
[0109]
For example, in the above embodiment, the plasma is in a constant state, but the plasma may be modulated by intermittently applying high-frequency power for plasma generation.
[0110]
The source gas is not limited to that in the above embodiment.
[0112]
  An organosilane gas containing F as one of the constituent elements is SiF (OCH₂ CF_Three)_Three, SiF (OCH₂C (OR)_Three)_Three(R is a functional group), SiF (OCH₂CF₂R)_Three(R is a functional group), SiF (OCH₂C (OR)₂R ′)_Three(R and R 'are functional groups), SiF (OCH₂C (NR₂)_Three)_Three(R is a functional group), SiF (OCH₂C (NR₂)₂R ′)_Three(R and R 'are functional groups), SiF (OCH₂ CRO)_Three(R is a functional group), SiF (OCH₂CN)_Three(R is a functional group), SiF (OCH₂NO₂)_Three, SiF (OCH₂COOR)_Three(R is a functional group), SiF_n(OCH₂CF₂R)_4-n(N = 1 to 3, R is a functional group)Can be used.
[0113]
The characteristic of organosilane gas containing F as one of the constituent elements is Si—O—CH.₂-To make the electrical state of the portion C into a stronger negative charge state. These gases can also be used without an oxidant gas as an organosilane gas containing F and O as constituent elements.
[0114]
In addition, as an inorganic silane gas containing F as a constituent element, SiF_nH_4-n(N = 1 to 4) or the like can be used.
[0115]
Moreover, as organosilane gas, TEOS, H_nSi (OC₂H_Five)_4-n(N = 1-3), H_nSi (OC_FourH₉)_4-n(N = 1 to 3) or the like can be used.
[0116]
As the inorganic silane gas, SiH_Four, Si₂H₆Etc. can be used.
[0117]
As the oxidant gas, O₂, N₂O or the like can be used.
[0118]
In addition, as a compound gas having N and B as one of constituent elements, NO, NH_Three, N₂H_Four, BH_Three, B₂H₆Etc. can be used.
[0119]
In the above embodiment, pure Al is used as the wiring material. However, other wiring material, for example, an alloy containing Al as a main component may be used. In addition, any one of copper (Cu), silver (Ag), gold (Au), nickel (Ni), palladium (Pd), platinum (Pt), or one or more of these elements as a main wiring material An alloy may be used.
[0120]
In addition, various modifications can be made without departing from the spirit of the present invention.
[0121]
【The invention's effect】
As detailed above, according to the present invention, SiO₂F-doped SiO with network structure₂In the film, even if the F concentration is increased, SiO having Si combined with two or more F that causes hygroscopic deterioration.₂Since the generation of network structure can be effectively suppressed, F-doped SiO with low hygroscopicity and low dielectric constant₂A membrane can be realized.
[Brief description of the drawings]
FIG. 1 shows SiF when the activation energy is changed under the condition of a constant film formation temperature._nO_{(4-n) / 2}The figure which shows the statistical distribution of (n = 1,2,3,4)
FIG. 2 shows SiF when the deposition temperature is changed under the condition of constant activation energy._nO_{(4-n) / 2}The figure which shows the statistical distribution of (n = 1,2,3,4)
FIG. 3 is a schematic diagram showing a schematic configuration of a plasma CVD apparatus used for forming an interlayer insulating film according to the first embodiment of the present invention.
FIG. 4 is a process cross-sectional view illustrating a method of forming an interlayer insulating film according to the first embodiment of the present invention.
FIG. 5 shows F and N-added SiO according to the present invention.₂Diagram showing hygroscopicity of membrane
FIG. 6 is a process cross-sectional view illustrating a multilayer wiring forming method according to a second embodiment of the present invention.
FIG. 7 is a schematic diagram showing a schematic configuration of a plasma CVD apparatus used for forming an interlayer insulating film according to a third embodiment of the present invention.
FIG. 8 is a process sectional view showing a multilayer wiring forming method according to a third embodiment of the present invention;
FIG. 9 is a process cross-sectional view illustrating a multilayer wiring forming method according to a fourth embodiment of the present invention.
FIG. 10 shows SiF with no activation energy increment._nO_{(4-n) / 2}(N = 1, 2, 3, 4) and Fl SiOSiF_mThe figure which shows the statistical distribution of (structure where F exists simultaneously in adjacent Si)
FIG. 11 shows SiF when the activation energy increment is 1.5 kcal / mol._nO_{(4-n) / 2}(N = 1, 2, 3, 4) and F_lSiOSiF_mThe figure which shows the statistical distribution of (structure where F exists simultaneously in adjacent Si)
FIG. 12 shows SiF when the activation energy increment is 3.0 kcal / mol._nO_{(4-n) / 2}(N = 1, 2, 3, 4) and F_lSiOSiF_mThe figure which shows the statistical distribution of (structure where F exists simultaneously in adjacent Si)
[Explanation of symbols]
10 ... Exhaust device
11 ... Semiconductor substrate
12 ... Board support
13 ... Resistance heater
14 ... Cooling pipe
15 ... High frequency power supply
16 ... deposition chamber
17 ... Counter electrode
18 ... Gate valve
19 ... High frequency power supply
20 ... F-added SiO₂film
21 ... Al wiring
22 ... F-added SiO₂film
23 ... Al wiring
24 ... F-added SiO₂film
31 ... Semiconductor substrate
32 ... BPSG membrane
33 ... Al wiring
34 ... Pure SiO₂film
35 ... F-added SiO₂film
36 ... Pure SiO₂film
37 ... Via Hall
38 ... Tungsten film
39 ... Al wiring
40 ... Pure SiO₂film
41 ... F-added SiO₂film
42 ... Pure SiO₂film
50 ... Deposition chamber
51. Semiconductor substrate
52. Substrate support base
53. Resistance heater
54 ... Cooling pipe
55. Exhaust device
56 ... Nozzle
57 ... High frequency coil
58 ... High frequency power supply
59 ... High frequency power supply
70 ... F, N added SiO₂film
71 ... Al wiring
72 ... F, N added SiO₂film
73 ... Al wiring
74 ... F and N added SiO₂film
80 ... F and B added SiO₂film
81 ... Al wiring
82 ... F and B added SiO₂film
83 ... Al wiring
84 ... F and B added SiO₂film

Claims (1)

When electrically insulating between conductive regions and forming an insulating film containing Si, O, F and having a network structure of SiO ₂ by a plasma CVD method,
As a raw material gas, the activation energy required for replacing the element bonded to Si with F is larger when F is bonded to Si than when F is not bonded to Si. , SiF (OCH ₂ CF ₃ ) ₃ , SiF (OCH ₂ C (OR) ₃ ) ₃ (R is a functional group), SiF (OCH ₂ CF ₂ R) ₃ (R is a functional group), SiF (OCH ₂ C ( OR) ₂ R ′) ₃ (R and R ′ are functional groups), SiF (OCH ₂ C (NR ₂ ) ₃ ) ₃ (R is a functional group), SiF (OCH ₂ C (NR ₂ ) ₂ R ′) ₃ (R and R ′ are functional groups), SiF (OCH ₂ CRO) ₃ (R is a functional group), SiF (OCH ₂ CN) ₃ , SiF (OCH ₂ NO ₂ ) ₃ , SiF (OCH ₂ COOR) ₃ (R functional groups) or _{SiF n (OCH 2 CF 2 R} ) 4-n (n = 1~3, R is the gas functional group) Used, and the two activation energy difference _{ΔE a [kcal / mol] (} > 0), the deposition temperature T [K], in the case where the Boltzmann constant was _{k B, · ΔE a / (} k B T) The method for manufacturing a semiconductor device, wherein the insulating film is formed under a condition that satisfies a condition of 1.5 × 10 ⁻³ .

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