JP3373705B2 - Semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having an insulating film for electrically separating conductive layers such as wirings.

[0002]

2. Description of the Related Art Conventionally, as an insulating film (interlayer insulating film) for electrically separating wirings of elements, thermally oxidized Si is used.
O ₂ film or silane or tetraethoxysilane (TEO
A SiO ₂ film formed by a CVD method at a reduced pressure or a normal pressure using a gas such as S) as a raw material gas is mainly used.

Particularly, for insulation between aluminum (Al) wirings, a SiO ₂ film formed by a plasma CVD method using a mixed gas of TEOS, O ₂ and O ₃ as a source gas is 400 ° C.
It is used because it can be formed at a low temperature.

By the way, in recent years, high integration of semiconductor elements,
As the speed increases, the problem of delay in signal transmission becomes noticeable.
The reason for this is that the time constant of signal transmission increases due to the synergistic effect that the inter-wiring capacitance (C) increases as the element becomes finer and the inter-wiring capacitance (C) increases, and the wiring resistance (R) increases due to the reduction in the wiring cross-sectional area. (RC delay).

RC delay is a main factor that hinders high-speed operation of semiconductor devices, and particularly hinders performance improvement of logic devices and high-speed SRAMs. As measures against this, Cu and Ag, which have a lower specific resistance than Al, are used as the wiring material to reduce the wiring resistance, and the relative dielectric constant of the insulating film interposed between the wirings is reduced to reduce the inter-wiring capacitance. Two points are important.

The relative permittivity of the SiO ₂ film formed by the conventional plasma CVD method is 4.0 to 5.0, which is a large value even compared with that of the thermally oxidized SiO ₂ film (3.9). I know that. Therefore, in order to reduce the relative permittivity, introduction of F into the SiO ₂ film has been studied, and it has been reported that the introduction of F actually reduces the relative permittivity.

As a method of introducing F, F ion implantation method,
A CVD method using SiF (OC ₂ H ₅ ) ₃ and H ₂ O, a method of adding a boric acid aqueous solution to a supersaturated aqueous solution of H ₂ SiF ₆ , and precipitating SiO ₂ in a liquid phase, FEOS, O ₂ and F A plasma CVD method or the like using a gas containing (CF ₄ , NF _3, etc.) is known.

Regarding the state of F in the SiO ₂ film, the formation of Si—F bonds has been confirmed by infrared absorption spectrum measurement. Further, F ₂ molecule or FO _x molecule (x = 2,
It is said that some of them are included as 3).

It has also been found that the density of the SiO ₂ film decreases as F is introduced.
The relative permittivity of the SiO ₂ film is reduced due to the synergistic effect with the decrease of the electronic polarizability and the ionic polarizability due to the generation of the F bond.

However, this type of F-added SiO ₂
The film (F-added SiO ₂ film) absorbs moisture when left in the atmosphere,
Due to this moisture absorption, new generation of Si—OH and desorption of F occur, which causes the relative permittivity to rise again and high-speed operation cannot be achieved. Moreover, F added S
The hygroscopicity of the iO ₂ film increases as the F concentration increases.

Further, the desorbed F diffuses to the wirings arranged in the upper and lower layers of the F-added SiO ₂ film, which causes corrosion of the wiring and deterioration of adhesion, resulting in a decrease in reliability. was there.

Incidentally, regarding the relationship between the F concentration in the F-added SiO ₂ film and the bonding state of F and the hygroscopicity, it is reported that the hygroscopicity sharply increases as the number of F atoms bonded to Si atoms increases. . Therefore, it has been studied to control the F bonding state in the SiO ₂ film and the local structure of the SiO ₂ network around the Si atom to which the F atom is bonded.

However, SiO ₂ film, especially F-added S
In the iO ₂ film, defects that deteriorate the moisture absorption resistance and Si
No report has yet been made to clarify the O ₂ network structure and control it.

[0014]

As described above, the F-added SiO ₂ film has been proposed as an insulating film having a low relative dielectric constant. However, due to the hygroscopicity of the F-added SiO ₂ film, the desorption of F occurs. This has occurred, which causes problems such that the relative permittivity is increased again and the wiring is corroded.

The present invention has been made in consideration of the above circumstances, and an object thereof is Si which can suppress hygroscopicity.
It is to provide a semiconductor device including an insulating film having an O ₂ network structure.

[0016]

In order to achieve the above object, a semiconductor device (claim 1) according to the present invention electrically separates conductive layers and contains at least Si, O and F , and SiO. _2. A semiconductor device comprising an insulating film having a network structure of ₂ , wherein defects due to O having a dangling bond that does not participate in crosslinking of the network structure, or O having this dangling bond captures an electron or a hole. defects due to it, before
A radius of 0.39 nm centered on the Si bonded to the element F
It is characterized by not existing within the area within .

Another semiconductor device according to the present invention (claim 2) is that at least the conductive layers are electrically separated from each other by at least S.
A semiconductor device including an insulating film having a network structure of SiO ₂ containing i, O and F , having dangling bonds that do not participate in crosslinking of the network structure, and having an electronegativity higher than Si. Defects caused by atoms, or defects caused by the atoms having this dangling bond capturing electrons or holes
Has a radius of 0.3 centered on the Si bonded to the F
It is characterized in that it does not exist in the region within 9 nm .

Another semiconductor device according to the present invention (claim 3) electrically separates the conductive layers, and at least S
What is claimed is: 1. A semiconductor device comprising an insulating film having a network structure of SiO ₂ , containing i, O, and F , having a dangling bond that does not participate in crosslinking of the network structure, and is a defect due to an atom that can serve as an electron donor. has a dangling bond not participating in the crosslinking of the network structure, and defects due to atom having a lone pair of electrons or defects due to the atoms having these dangling bonds trapping electrons or holes, wherein F is Before combined
It exists in the area within a radius of 0.39 nm centered on Si.
It is characterized by not existing .

Another semiconductor device according to the present invention (claim 4) is characterized in that, in the semiconductor device (claims 1 to 3), the insulating film contains N or B.

The reduction amount of the above defects is not particularly limited, but is appropriately determined for each system using the insulating film.

As a method of forming the insulating film, for example, plasma CVD method may be used. At this time, the substrate temperature is preferably set within a range of 350 to 550 ° C. at which dehydration condensation of the structural water taken into the insulating film becomes remarkable.

As the raw material gas, an organic silane gas, an oxidizing gas and a compound gas containing F as one of the constituent elements, an inorganic silane gas, an oxidizing gas and a compound gas containing F as one of the constituent elements, and an oxidizing agent are used. An organic silane gas containing gas and F as one of the constituent elements, an inorganic silane gas containing oxidant gas and F as one of the constituent elements, and an organic silane gas containing F and O as constituent elements are used.

Here, as the compound gas containing F as one of the constituent elements, specifically, NF ₃ , CF ₄ , and C are used.
₂ F ₆ , ClF ₃ , SiF _{4 and the} like can be mentioned.

The organic silane gas containing F as one of the constituent elements is specifically SiF (OC
₂ H ₅ ) ₃ , SiF ₂ (OC ₂ H ₅ ) ₂ , SiF ₃ (O
C ₂ H ₅ ) and the like. These gases can be used as an organic silane gas containing F and O as constituent elements without an oxidant gas.

As the inorganic silane gas containing F as one of the constituent elements, specifically, SiH ₃ F, SiH ₃ F
₂ , SiHF _{3 and the} like.

Specific examples of the organic silane gas include TEOS, HSi (OC ₂ H ₅ ) ₃ and H ₂ Si (O
Such as C ₄ H _{9) 2} and the like.

Specific examples of the inorganic silane gas include SiH ₄ and Si ₂ H ₆ .

Further, as the oxidant gas, specifically,
Examples include O ₂ and H ₂ O.

[Function] In the study of the moisture absorption resistance of the SiO ₂ film, the present inventor reduced the specific defects, that is, the defects described in claims 1 to 3, thereby reducing the conventional S
It was found that the hygroscopicity can be made lower than that of the iO ₂ film.

Therefore, according to the present invention, it is possible to prevent an increase in the relative dielectric constant due to moisture absorption. In particular, in the case of an insulating film containing F, the hygroscopicity can be reduced while the reduction of the relative dielectric constant due to F is maintained. As a result, it is possible to prevent a reduction in inter-wiring capacitance and an increase in signal delay, and to realize a high-speed operation element.

[0031] By reducing the defect, the reason can be lowered hygroscopicity, when no said specific defects, H ₂ O adsorption is effectively caused by the increase of the adsorption energy of H ₂ O This is because it is suppressed.

Further, according to the research by the present inventor, in the case of an insulating film containing F, when the above defects are not present within a radius of 0.39 nm around the Si atom to which the F atom is bonded,
It was found that the new reaction between F and H ₂ O accompanying the promotion of H ₂ O adsorption is effectively suppressed. The size of this defect-free region is determined by the free volume (void) required for the transition state formation and the adsorption of a plurality of H ₂ O during the moisture absorption process.

[0033]

DETAILED DESCRIPTION OF THE INVENTION

(Experiment / Consideration) First, the experiment and its consideration, which are the basis of the invention, will be described. 1 and 2, S
O having an unbonded hand that is not involved in crosslinking of the iO ₂ network structure
The results of the ab initio molecular orbital method using a cluster model showing the adsorption / hydrolysis process of H ₂ O depending on the presence / absence of a defect due to an atom (non-bridging oxygen) capturing an electron are shown.

Was adopted cluster models H ₂ O attacks ^- [0034] As a model considering the adsorption and hydrolysis process model and FSi (OH) ₂ O to attack FSi (OH) ₃ Cluster H ₂ O is.

The former model is the F-doped Si without the above defects.
FSiO simulating O ₂ and containing F-bonded Si
_A trihedral unit is cut out from bulk F-added SiO ₂ and three O dangling bonds generated at that time are terminated by virtual H.

The latter model is a state in which the bridge of one bridging O atom to the adjacent SiO ₄ tetrahedral unit is cut (in the model, one H of OH is removed) and the electron is captured in the former model. It simulates the F-added SiO ₂ with the defect.

It was revealed from the analysis by the inventor's ab initio molecular orbital method that such a defect site is easily formed when Si having two F atoms bonded thereto reacts with OH ^−. There is. Further, as reported that non-bridging oxygen is stabilized by capturing electrons, the non-bridging oxygen generated during film formation may be electrically trapped and formed.

FIG. 1 shows a single H ₂ O moisture absorption process, FSi.
The total energy changes of (OH) ₃ + H ₂ O and FSi (OH) ₂ O ⁻ + H ₂ O are shown.

Here, the total energy of the progenitor system corresponding to the dissociation limit of FSi (OH) ₃ and H ₂ O or FSi (OH) ₂ O ⁻ and H ₂ O is used as the energy reference.

The total energy of the accompanying system approach of FSi (OH) ₃ in H ₂ O is reduced gradually, the adsorption state of the H ₂ O is formed. Adsorption energy is about 11 kcal / mo
It is l. This value is almost equal to the hydrogen bond formation energy. In addition, the three natural vibration modes of H ₂ O in this adsorption state are ν ₁ ↓ as compared with the case of isolated H ₂ O.
(Decrease), ν ₂ ↑ (increase), ν ₃ ↓ (decrease). This shift is equivalent to the shift during H ₂ O multimer formation. Therefore, it can be seen that the state is an adsorption state due to hydrogen bond formation.

Then, the lone electron pair localized on O of the adsorbed H ₂ O is coordinated to Si in a conformation such that a new Si-O bond is formed, and at the same time, one H ₂ O of H ₂ O is coordinated. Are attracted to F and the F-H bond is strengthened, forming a transition state [HFSi (OH) ₄ ] ^≠ from H ₂ O insertion to HF desorption.

There is an activation barrier of about 41 kcal / mol in this process, and it is considered that the barrier cannot be easily crossed near room temperature. The sharp weakening of the H-OH bond was confirmed by the result of the decrease in the force constant.

Then, the Si--F bond is rapidly extended, and F--
Reaction intermediate [HFSi (O
H) ₄ ] ^≠ is formed. This metastable reaction intermediate stabilizes to the energy level between the prototypical system and the H ₂ O adsorbed state.

In this state, the distorted Si (OH) ₄ is converted into HF.
Can be regarded as adsorbed. This is confirmed by the fact that the natural vibration mode of HF shifts to the lower wave number side as compared with the isolated HF.

After this, F is desorbed as HF, and Si (O
A production system is formed in which H) ₄ remains. This process is an endothermic reaction of about 12 kcal / mol corresponding to the adsorption energy of HF. However, if the above transition state can be exceeded, it can be easily exceeded if the dissipation of the large emitted energy is relatively slow.

Here, the change in the hydrolysis process due to the difference in the number of F bonds per Si atom will be shown by paying attention to the change in the potential energy of the reaction, particularly the change in the adsorption energy / activation energy.

Model system, SiF _n (OH) _4-n + H ₂ O
A comparison of the total energy changes (n = 0-3) was investigated by the ab initio molecular orbital method. The adsorption energies were all about 11 kcal / mol and did not depend on the F bond number.

As a result of examining each adsorption structure, it was found that the hydrogen bond between H ₂ O and the cluster corresponds to the formation of O ... H-OH rather than F ... H-OH. .

The activation energy of the H ₂ O insertion reaction is F
From 0 to F1 about 37 kcal / mol to about 4 kca
After increasing l / mol, about 3-4k with increasing number of F bonds
It gradually decreases by cal / mol.

[0050] That is, the structure F1 pieces are bonded to Si, when the H ₂ O insertion reaction than SiO ₂ containing SiO ₂ or silanol groups of the non-doping is but is suppressed, further F bond number is increased reverse Be promoted to.

Assuming an Arrhenius type reaction rate constant in the vicinity of room temperature, an acceleration effect of about three digits is obtained. The reaction intermediates for HF elimination are HF except for the case of F0.
It can be regarded as an adsorbed state, which is an adsorbed state due to a hydrogen bond between F of FH and O of OSi.

Therefore, the desorption energy is 10 to 11
kcal / mol, independent of the number of F bonds.

On the other hand, in the case of FSi (OH) ₂ O ⁻ , the total energy of the system is F _n Si (OH) _{4 −n} (n = 0 to 3) including FSi (OH) ₃ as H ₂ O approaches. It is much more greatly reduced and an adsorbed state of H ₂ O is formed. The adsorption energy reaches about 19 kcal / mol, which is about double.

[0054] Then, one of H of the adsorption H ₂ O is O ^- to be drawn -O ^- ... stronger binding of H, transition state to H drawing _{[FSi (OH) 2 OHOH]} - forming a ^≠.
There is only an activation barrier of about 7 kcal / mol in this process, and it can be easily crossed near room temperature due to the release of adsorption energy.

[0055] Then, the H-OH bond is stretched, -O ^- ...
Reaction intermediate with strengthened H bonds [FSi (OH) ₂ OH
OH] ⁻ is formed. This metastable reaction intermediate is slightly stabilized from the transition state to H abstraction.

Further, the H-OH bond is extended to form a triangular bipyramidal reaction intermediate [FSi (OH) ₄ ] ^{-, which} is stable up to the energy level between the above-mentioned precursor system and the H ₂ O adsorbed state. Turn into.

After that, an endothermic reaction of 40 to 70 kcal / mol or more is required to form a production system in which F ⁻ or OH ⁻ is desorbed, and an endothermic reaction also occurs in the overall reaction system. Therefore, it is believed that the reaction ends at either reaction intermediate stage.

FIG. 2 shows the moisture absorption process of _two H ₂ O, FSi.
(OH) ₃ + 2H ₂ O, FSi (OH) ₂ O ⁻ + 2H ₂
The total energy change of O is shown.

The total energy of the progenitor system corresponding to the dissociation limit between FSi (OH) ₃ and H ₂ O 2 or FSi (OH) ₂ O ⁻ and H ₂ O 2 is taken as the energy reference.

[0060] In FSi (OH) ₃ In two H ₂ O is separate, i.e., adsorption state (adsorption energy of H ₂ O to adsorb in the absence of interaction between the H ₂ O is about 17Kcal /
mol), the interaction between H ₂ O is strong, and it is adsorbed in a state close to a dimer (adsorption energy is about 25
kcal / mol) is possible.

Next, a transition state [HFSi (OH) ₄ (HOH)] ^≠ from H ₂ O insertion to HF desorption is formed.
Since the interaction between H ₂ O is weakened in the transition state, it is considered that the transition from the dimer adsorption to the transition state occurs via the individual adsorption state. The activation barrier from the individual adsorption state is about 28 kcal / mol.

Compared to FIG. 1, the activation barrier is H ₂ alone.
About 41 kcal / mol to about 28 kcal with O insertion
/ Mol down to about 70%. The activation barrier is still high, but it is thought that it can be exceeded even at room temperature if the dissipation of the increased adsorption energy is relatively slow.

Then, the Si--F bond rapidly expands, and F
Reaction intermediate [HFSi (OH) _{4 with} enhanced -H bond
(HOH)] is formed. This metastable reaction intermediate stabilizes to an energy level approximately equal to the individual adsorption state of H ₂ O. In this state, the distorted Si (OH) ₄ becomes H ₂
It is considered that O is slightly strong and HF is weakly adsorbed. F
There eliminated as HF, Si (OH) ₄ first intermediate H ₂ O is adsorbed is formed on, then the product system H ₂ O is desorbed is formed. This process is about 12, 11 respectively
It is an endothermic reaction of kcal / mol.

However, when the above transition state is exceeded, it is considered that if the dissipation of the large emitted energy is relatively slow, it can be exceeded even near room temperature. In particular, up to the stage where HF is desorbed and the first intermediate in which H ₂ O is adsorbed on Si (OH) ₄ is formed, the reaction system is slightly exothermic. Therefore, the second H
It can be considered that ₂ O can catalytically accelerate the hydrolysis process.

On the other hand, two cases are considered for FSi (OH) ₂ O ⁻ .

In the first case, as described in the explanation of FIG. 1, after the first H ₂ O interacts with FSi (OH) ₂ O ⁻ , the second H ₂ O interacts. This is the case.
In the second case, two H ₂ O are simultaneously FSi (OH) ₂
When interacting with O ⁻ , that is, FSi (OH) ₂
This is the case where the free volume (void) around O ⁻ is large.

First, in the first case, the first H ₂ O interacts with FSi (OH) ₂ O ⁻ and, after the transition state has passed, two kinds of reaction intermediates, that is, [FSi (OH) ₂ OH
OH)] ^- , a triangular bipyramidal reaction intermediate [FSi (O
H) _4] ^- it is formed.

In this case, the total energy starting from the dissociation limit of each of the two kinds of reaction intermediates and H ₂ O is changed to the energy standard. With the approach of H ₂ O to these two types of reaction intermediates, the total energy of the system is greatly reduced and a second H ₂ O adsorption state is formed. Adsorption energies are about 25 and about 21 kcal, respectively
/ Mol, H which is close to the dimer to FSi (OH) ₃ .
_It is almost equal to the adsorption state of ₂ O.

Next, the second case will be described. In this case, the total energy with the dissociation limit between FSi (OH) ₂ O ⁻ and H ₂ O ₂ being the primary system is taken as the energy standard.

An interaction state (adsorption energy of about 36 kcal / mol) is possible in which FSi (OH) ₂ O ⁻ is adsorbed in a state where the interaction between _two H ₂ O is strong and is close to a dimer. This is a H ₂ O close to a dimer to FSi (OH) ₃ .
It reaches about 1.5 times the adsorption energy in the adsorption state.

The above results are summarized in the following table, focusing on the adsorption energy and the activation energy.

[0072]

[Table 1]

To summarize the above, an O atom having a dangling bond (non-bridging oxygen) that does not participate in the crosslinking of the SiO ₂ network structure
Alternatively the O-atom when a defect is shown in a state in which capture electrons exist, firstly, the adsorption energy of H ₂ O is increased H ₂ O adsorption is promoted. In addition, H ₂ after adsorption
The activation barrier to the O dissociation / addition reaction decreases, and the barrier height can easily be exceeded even near room temperature. Therefore,
Achieving a SiO ₂ network structure that does not include the above defects is effective in suppressing moisture absorption. Similarly, a SiO ₂ network structure containing no defects, which is shown in a state where the O atom traps holes, is also effective in suppressing moisture absorption. From this result, it can be seen that the defect due to the O atom is
O ₂ network structure has a dangling bond that is not involved in crosslinking, a state in which the atom captures an electron or a hole, an atom that can serve as an electric donor or an atom having a lone pair of electrons is Si.
A state in which there are dangling bonds that are not involved in cross-linking of the O ₂ network structure, a state in which the atom in the state captures an electron or a hole,
Considering that it can be regarded as a defect represented by any of the above, achievement of a SiO ₂ network structure free of such defects is effective for suppressing moisture absorption.

The minimum size of this defect-free region is the transition state formation and the formation of a plurality of H ₂ O during the moisture absorption process.
It is determined from the free volume (void) required for adsorption. In particular,
Radius 0.39n centered on Si atom to which F atom is bonded
SiO having a local structure not having the above defects within m
_In the case of the _second network structure, the reaction between new F atoms and H ₂ O associated with the promotion of H ₂ O adsorption is suppressed. The radius of 0.39 nm was set as a value obtained by adding an F ⁻ ion radius of 0.07 nm to the Si—F bond length of 0.32 nm.

(First Embodiment) FIG. 3 shows the first embodiment of the present invention.
Plasma C used for forming the interlayer insulating film according to the embodiment
It is a schematic diagram which shows schematic structure of a VD apparatus. In this embodiment, SiF (OC ₂ H ₅ ) ₃ , O ₂ and S are used as raw material gases.
A mixed gas of iH ₄ and TEOS is used. The characteristic of this source gas is that it contains SiH ₄ .

Next, a method of forming a multi-layer wiring using the above plasma CVD apparatus will be described. First, the semiconductor substrate 1 on which elements are formed is set on the substrate support base 2. Next, the semiconductor substrate 1 is heated to a predetermined temperature by the resistance heater 3 provided in the substrate support base 2 and set to a predetermined substrate temperature (heating temperature). A cooling pipe 4 for circulating a cooling agent is provided in the substrate support base 2 to prevent the substrate temperature from becoming a high temperature exceeding a predetermined temperature.

The substrate temperature (heating temperature) is the thermal desorption spectrum (TDS) previously performed.
In the measurement of (copy), dehydration condensation of structural water (Si—OH, HOH) taken in SiO ₂ becomes remarkable 350
It is preferable to set the temperature within the range of to 550 ° C. Here, the substrate temperature is set to 470 ° C.

[0078] Thus, the free volume required achieve densification of the SiO ₂ network, and the extension of relaxation and Si-F of SiO ₂ network by structural water residual (void)
Can be suppressed.

Next, in the film forming chamber (reaction vessel) 6, TEOS as a source gas is 50 cm ³ / min and O ₂ is 50.
0 cm ³ / min, 0 to 50 SiF (OC ₂ H ₅ ) ₃
0 cm ³ / min and SiH ₄ are simultaneously introduced at a flow rate of 50 cm ³ / min, and the pressure in the film forming chamber 6 is maintained at 133 Pa by the exhaust device 10. The flow rate is adjusted by the gate valve 11.

Next, the RF power of 13.56 MHz is applied to the electrode 7 facing the semiconductor substrate 1 by the high frequency power source 12 for 1 k.
W is applied to start discharge, and at the same time, 350 kHz is applied to the substrate support base 2 by the high frequency power source 5 provided on the substrate support base 2.
By applying the RF bias of 500 W, the SiO ₂ film (F-added SiO ₂
Film) is formed.

At this time, S which may be taken into the interlayer insulating film
Electrons or ions (typically, having an energy capable of giving energy of about 12 to 25 eV or more, which is the energy required to break the O—H bond of i-OH or H—OH, to the surface of the interlayer insulating film during film formation (typically, By irradiating the surface of the interlayer insulating film being formed with F ^± , O ^± , and O ₂ ^± ions), decomposition of Si—OH on the film surface is promoted and the SiO ₂ network is densified.

The non-bridging oxygen (defects) that can be generated during the film formation is due to the densification of the network by oxygen ion irradiation and S
iH ₄ is decomposed by termination with SiH _n (n = 1 to 3).

Thus, as shown in FIG. 4A, the F-doped SiO ₂ film 8 having a thickness of 500 nm is formed as an interlayer insulating film on the semiconductor substrate 1 on which the semiconductor element is formed.

Next, as shown in FIG. 9A, after an Al film is formed on the F-added SiO ₂ film 8 by DC magnetron sputtering, the Al film is patterned to have a wiring width of 500 nm and a wiring thickness of 400 nm. The Al wiring 9 of the first layer is formed.

Next, as shown in FIG. 4B, F-added Si
800-nm-thick F-doped Si using the same film formation method as the O ₂ film 8
After forming the O ₂ film 14, an Al film having a thickness of 400 nm is formed as in the case of the Al wiring 9, and the Al film is patterned to form the second-layer Al wiring 15.

Finally, as shown in FIG. 9B, an F-added SiO ₂ film 16 having a thickness of 800 nm is formed by the same film forming method as that of the F-added SiO ₂ film 8.

It was confirmed by infrared absorption spectrum measurement that F was added to form a Si--F bond. This infrared absorption spectrum shows about 1080 cm ^-1 , about 800
cm ^-1, the other absorption peak attributable to SiO ₂ specific normal vibrational mode at about 450 cm ^-1, Si at about 935cm ^-1
An absorption peak attributed to the -F bond was observed. Also,
The F atom concentration in this F-added SiO ₂ film is about 10 at%.
The refractive index was 1.43 and the relative dielectric constant was 3.3.

Further, in the present embodiment, as a plasma CVD apparatus, the discharge in the deposition chamber is carried out by applying a high frequency to the electrode facing the semiconductor substrate.
Although the apparatus is used, another CVD apparatus may be used.

For example, a conventionally used parallel plate type plasma CVD apparatus or a CVD apparatus capable of forming a high density plasma of 1 × 10 ¹¹ ions / cm ³ or more such as microwave discharge or magnetron discharge, for example, cyclotron resonance is used. The conditions at the time of forming the insulating film can be controlled even by using the above-described plasma CVD apparatus, plasma CVD apparatus using dielectric current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate CVD apparatus. As a result, an F-doped SiO ₂ film similar to that of this embodiment can be formed.

FIGS. 5 (a) and 5 (b) show the moisture absorption of the F-added SiO ₂ film formed by the method of the embodiment. It is the result of measuring the infrared absorption spectrum change.

In the figure, the horizontal axis represents the concentration of added F (Si-F
/ Corresponding to SiO ratio) is a value obtained by normalizing the Si-F stretching peak integrated intensity of about 935cm ^-1 in SiO ₂ antisymmetric stretching peak integrated intensity of about 1080 cm ^-1. The vertical axis corresponds to the absorption is a structural water concentrations incorporated into _{SiO 2 ((Si-OH,} H-OH) / SiO ratio), Si-OH in about 3750~3000cm ^-1, H-OH It is a value in which the peak integrated intensity is standardized by the SiO ₂ antisymmetric expansion / contraction peak integrated intensity of about 1080 cm ⁻¹ .

From FIG. 9, it can be seen that the amount of structured water decreases immediately after the deposition and the amount of moisture absorption after standing in the air decreases. When the F concentration is low (less than 2%), the amount of moisture absorption is increased because it is considered that a large number of OH groups are present in the film. Furthermore, by FT-IR, S in the film
The fact that the symmetry of the peak due to the i-F bond is not significantly broken indicates that the formation of a structure in which one Si has two or more Fs is suppressed. When a film was formed by changing the film forming temperature, the above effect was not obtained when the film forming temperature was 400 ° C. or lower. From this result, it is desirable that the temperature during film formation is 400 ° C. or higher.

A film formed at 400 ° C. or higher is
Si-F spectrum of the film formed below ℃ FT-IR
As a result of the comparison, it was found that it is desirable that the ratio of Si atoms having two or more Fs bonded is 1/3 or less at most with respect to the Si atoms having one or more Fs bonded.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention.
FIG. 6 is a process cross-sectional view showing the method for forming multilayer wiring according to the embodiment. In order to improve hygroscopicity, a laminated insulating film of an F-added SiO ₂ film (F-added SiO ₂ film) and a non-F-added SiO ₂ film (pure SiO ₂ film) is used as an interlayer insulating film. This is the example used.

First, as shown in FIG. 6A, a boron phosphorus glass film (BPSG film) 22 having a thickness of 800 nm is formed on a semiconductor substrate 21 on which elements are formed. Then 400
nm Al film is formed by the sputtering method.
The l film is patterned to form the first-layer Al wiring 23.

Next, as shown in FIG. 6B, plasma CV using a mixed gas of TEOS and O ₂ as a source gas.
After the pure SiO ₂ film 24 having a thickness of 100 nm is formed by the D method, TE gas is used as a source gas as in the first embodiment.
A thickness of 500 n was obtained by a plasma CVD method using a mixed gas of OS, O ₂ , SiH ₄ and SiF (OC ₂ H ₅ ) _3.
An F-added iO ₂ film 25 of m is formed. Next, plasma CV using a mixed gas of TEOS and O ₂ as a source gas
A pure SiO ₂ film 26 having a thickness of 100 nm is formed by the D method.

Next, as shown in FIG. 6C, a resist (not shown) is applied on the entire surface, exposed and developed to form a resist pattern, and then dry etching is performed using this resist pattern as a mask. A via hole 27 is opened in the insulating films 24, 25 and 26 on the Al wiring 23.

Next, as shown in FIG. 6D, selective CVD using a mixed gas of WF ₆ and SiH ₄ as a source gas.
Method or non-selective CVD method and chemical mechanical polishing or resist etch back are combined to fill the via hole 27 with the tungsten film 28.

Next, as shown in FIG.
nm Al film is formed by a sputtering method, and the Al film is patterned to form a second-layer Al wiring 29. Then, a pure SiO ₂ film 30 having a thickness of 100 nm and a thickness of 500 n are formed.
m F-added SiO ₂ film 31, 100 nm thick pure SiO
_{2 The} film 32 is sequentially formed.

The pure SiO ₂ film has a lower hygroscopic property than the F-added SiO ₂ film. Therefore, according to the present embodiment,
The moisture absorption of the interlayer insulating film can be further suppressed as compared with the first embodiment, and the decrease in reliability represented by the increase of the dielectric constant and the corrosion of the wiring can be effectively prevented. Instead of the pure SiO ₂ film, SiO having a low F concentration in the film and exhibiting no hygroscopic property
The same effect was obtained by using ₂ .

(Third Embodiment) FIG. 7 shows a third embodiment of the present invention.
Plasma C used for forming the interlayer insulating film according to the embodiment
It is a schematic diagram which shows schematic structure of a VD apparatus. In this embodiment, SiF (OC ₂ H ₅ ) ₃ , O ₂ and S are used as raw material gases.
A mixed gas of iH ₄ , NF _3, and TEOS is used.

In the figure, reference numeral 40 denotes a film forming chamber (reaction container) made of an insulating material. Inside the film forming chamber 40, a substrate support 4 for mounting a semiconductor substrate 41.
2. A nozzle 46 for introducing the source gas into the film forming chamber 40 is provided. Further, an exhaust device 45 is provided below the film forming chamber 40.
The inside of the film forming chamber 40 can be evacuated.

The substrate support 42 is provided with a resistance heater 43 which is an internal heater and a cooling pipe 44 for circulating a coolant. A high frequency power source 49 is connected to the substrate support table 42. Film forming chamber 40
A high frequency coil 47 is wound around the side wall of the, and a high frequency power source 48 is connected to the high frequency coil 43. Next, a method of forming a multi-layer wiring using the above plasma CVD apparatus will be described. First, the semiconductor substrate 4 on which elements are formed
1 is set on the substrate support 42, and the resistance heater 44
The substrate is heated to 470 ° C. The heating temperature is the thermal desorption spectrum (TDS: Thermal Desorp
In the ionization spectroscopy measurement, it is set within the range of 350 to 550 ° C. at which the dehydration condensation of the structural water (Si—OH, HOH) taken into SiO ₂ becomes remarkable.

[0104] Thus, it is possible to realize the suppression of formation of achieving densification of the SiO ₂ network, and free volume due to structural water remaining required extension of relaxation and Si-F of SiO ₂ network (void).

Next, in the film forming chamber 40, as source gas, TEOS is 50 cm ³ / min and O ₂ is 500 cm.
³ / min, SiH ₄ 50 cm ³ / min, NF ₃ 500 cm ³ / min, SiF (OC ₂ H ₅ ) ₃ 0 to
It is introduced simultaneously at a flow rate of 500 cm ³ / min so that the pressure in the film forming chamber 40 can be maintained at 133 Pa.

Next, 13.56 MHz RF power is applied to the high frequency coil 47 on the side wall of the film forming chamber 40 to start discharge, and at the same time, the substrate support table 42 is subjected to RF of 350 kHz.
A bias of 500 W is applied from the high frequency power source 49 to form an interlayer insulating film.

At this time, S which may be taken into the interlayer insulating film
Energy required for breaking O-H bond of i-OH and H-OH
Energy of about 12 to 25 eV, which is the energy
Of electrons or ions that have energy that can be applied to the film surface of
(Typically F^±, O^± , O₂ ^±Ion) is being formed
By irradiating the surface of the interlayer insulating film of
SiO that promotes the decomposition of Si-OH₂Precise network
Turn into.

The non-bridging oxygen (defects) that can be generated during film formation is due to network densification due to oxygen ion irradiation and S
iH ₄ decomposition product SiH _n (n = 1 to 3) and termination.

Thus, as shown in FIG. 8A, Si having a thickness of 500 nm and doped with F and N is formed on the semiconductor substrate 41.
An O ₂ film (F, N-added SiO ₂ film) 50 is formed.

Next, as shown in FIG. 8B, after forming an Al film by DC magnetron sputtering, the Al film is patterned to form a first layer Al wiring 51 having a wiring width of 500 nm and a wiring thickness of 400 nm. To form.

Next, as shown in FIG. 8C, an F, N-added SiO ₂ film 52 having a thickness of 800 nm is formed by the same film forming method as the F, N-added SiO ₂ film 50. Then, similarly to the case of the Al wiring 51, an Al film having a thickness of 400 nm is formed, and this Al film is patterned to form the second-layer Al wiring 53. Finally, F, in the same film forming method as N added SiO ₂ film 50, a thickness of 800 nm F, N added SiO ₂
The film 54 is formed.

In the present embodiment, as the plasma CVD apparatus, a CVD apparatus is used which discharges in the film forming chamber by applying high frequency power to electrodes provided on the side wall of the film forming chamber. A CVD device may be used.

For example, a conventional parallel plate plasma CVD apparatus or a CVD apparatus capable of forming high density plasma of 1 × 10 ¹¹ ions / cm ³ or more such as microwave discharge or magnetron discharge, for example, cyclotron resonance is used. The conditions at the time of forming the insulating film can be controlled even by using the above-described plasma CVD apparatus, plasma CVD apparatus using dielectric current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate CVD apparatus. As a result, an F, N-added SiO ₂ film similar to that of this embodiment can be formed.

(Fourth Embodiment) FIG. 9 shows a fourth embodiment of the present invention.
FIG. 6 is a process cross-sectional view showing the method for forming a multilayer wiring according to the embodiment of FIG. In the present embodiment, SiF (OC
A mixed gas of ₂ H ₅ ) ₃ , O ₂ , SiH ₄ , BF _3, and TEOS is used. Further, the same plasma CVD apparatus as that of the third embodiment is used as a film forming apparatus for the interlayer insulating film.

First, similarly to the third embodiment, the semiconductor substrate 41 on which the elements are formed is set on the substrate support base 42,
Heat to 470 ° C. with a resistance heater. The heating temperature is the thermal desorption spectrum (TDS)
In the absorption spectroscopy measurement, it is set within the range of 350 to 550 ° C. where the dehydration condensation of the structural water (Si—OH, HOH) taken into SiO ₂ becomes remarkable.

[0116] Thus, it is possible to realize the suppression of formation of achieving densification of the SiO ₂ network, and free volume due to structural water remaining required extension of relaxation and Si-F of SiO ₂ network (void).

Next, in the film forming chamber 40, as source gas, TEOS is 50 cm ³ / min and O ₂ is 500 cm.
³ / min, SiH ₄ is 50 cm ³ / min, BF ₃ is 500 cm ³ / min, SiF (OC ₂ H ₅ ) ₃ is 0-
It is introduced at a flow rate of 500 cm ³ / min at the same time so that the internal pressure of the film forming chamber 40 can be maintained at 133 Pa.

Next, RF power of 13.56 MHz is applied to the RF coil 47 on the side wall of the film forming chamber 40 by the RF power source 49.
Is applied to start discharge, and at the same time, the substrate support 42
Then, an RF bias of 350 kHz is applied by a high frequency power source 49 for 500 W to form an interlayer insulating film.

At this time, S which may be taken into the interlayer insulating film
Electrons or ions (typically, having an energy capable of giving energy of about 12 to 25 eV or more, which is the energy required to break the O—H bond of i-OH or H—OH, to the surface of the interlayer insulating film during film formation (typically, By irradiating the surface of the interlayer insulation during film formation with F ^± , O ^± , and O ₂ ^± ions, the decomposition of Si—OH on the film surface is promoted and the SiO ₂ network is densified.

The non-bridging oxygen (defects) that can be generated during the film formation is due to the densification of the network by oxygen ion irradiation and S
iH ₄ is decomposed by termination with SiH _n (n = 1 to 3).

Thus, as shown in FIG. 9A, Si having a thickness of 500 nm on which F and B are added is formed on the semiconductor substrate 41.
An O ₂ film (F, B-added SiO ₂ film) 60 is formed.

Next, as shown in FIG. 9B, after forming an Al film by DC magnetron sputtering, this Al film is patterned to form a first layer Al wiring 61 having a wiring width of 500 nm and a wiring thickness of 400 nm. To form.

Next, as shown in FIG. 9C, an F, B-added SiO ₂ film 52 having a thickness of 800 nm is formed by the same film forming method as the F, B-added SiO ₂ film 60, and then Al wiring is formed. 6
After forming an Al film having a thickness of 400 nm as in the case of 1, the Al film is patterned to form the second-layer Al wiring 63. Finally, the F, B-added SiO ₂ film 64 having a thickness of 800 nm is formed by the same film forming method as the F, B-added SiO ₂ film 60.

In the present embodiment, as a plasma CVD apparatus, the CVD in the film forming chamber is performed by applying a high frequency to the electrode facing the semiconductor substrate.
Although the apparatus is used, another CVD apparatus may be used.

For example, a conventional parallel plate type plasma CVD apparatus or a CVD apparatus capable of forming high density plasma of 1 × 10 ¹¹ ions / cm ³ or more such as microwave discharge or magnetron discharge, for example, cyclotron resonance is used. The conditions at the time of forming the insulating film can be controlled even by using the above-described plasma CVD apparatus, plasma CVD apparatus using dielectric current, plasma CVD apparatus using helicon wave, dipole ring magnetron plasma CVD apparatus or magnetron parallel plate CVD apparatus. As a result, an F, B-added SiO ₂ film similar to that of the present embodiment can be formed.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the raw material gases are TEOS, O ₂ , SiH ₄ and SiF (OC ₂ H
₅ ) ₃ was used, but it is not limited to this.

For example, as a compound gas containing F as one of the constituent elements, NF ₃ , BF ₃ , CF ₄ , C ₂ F ₆ , C
lF _3, SiF ₄ or the like may be used.

As the organic silane gas containing F as one of the constituent elements, SiF (OC ₂ H ₅ ) ₃ , SiF
₃ (OC ₂ H ₅ ) ₂ or SiF ₃ (OC ₂ H ₅ ) may be used. These gases can be used as an organic silane gas containing F and O as constituent elements without an oxidant gas.

Further, as the inorganic silane gas containing F as one of the constituent elements, SiH ₃ F, SiH ₂ F ₂ , SiHF
₃ or the like may be used. TEO as organic silane gas
S, HSi (OC ₂ H ₅ ) ₃ , H ₂ Si (OC ₄ H ₉ )
₂ or the like may be used.

As the inorganic silane gas, Si is used.
H ₄ , Si ₂ H ₆ or the like may be used. Further, O ₂ , N ₂ O or the like may be used as the oxidant gas.

Compound gases containing N and B as one of the constituent elements are NO, NH ₃ , N ₂ H ₄ , BH ₃ and B.
₂ H ₆ or the like may be used.

In the above embodiment, pure Al is used as the wiring material, but other wiring materials such as Al are used.
An alloy containing as a main component may be used. In addition, copper (Cu), silver (Ag), gold (Au), nickel (Ni), palladium (Pd), or platinum (Pt), or one or more of these elements are used as the main wiring material. It may be an alloy.

[0133]

As described in detail above, according to the present invention, S
In the insulating film having the iO ₂ network structure, the hygroscopicity can be improved by reducing the specific defects, so that the increase in the relative dielectric constant due to the moisture absorption can be prevented.

[Brief description of drawings]

FIG. 1 FSi (OH) ₃ + H ₂ in the hydrolysis process
Characteristic diagram showing total energy change of O type and FSi (OH) ₂ O ⁻ + H ₂ O type

FIG. 2 FSi (OH) ₃ + 2H in the hydrolysis process
Characteristic diagram showing total energy change of ₂ O type and FSi (OH) ₂ O ⁻ + 2H ₂ O type

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 showing the method for forming an interlayer insulating film according to the first embodiment of the present invention.

FIG. 5 is a diagram showing hygroscopicity of an F, N-added SiO ₂ film according to the present invention.

FIG. 6 is a process cross-sectional view showing the method for forming a multilayer wiring according to the 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 method for forming an interlayer insulating film according to a third embodiment of the present invention.

FIG. 9 is a process cross-sectional view showing the method for forming a multilayer wiring according to the fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2 ... Substrate support 3 ... Resistive heater 4 ... Cooling pipe 5 ... High frequency power source 6 ... Deposition chamber 7 ... Electrode 8 ... F-added SiO ₂ film 9 ... Al wiring 10 ... Exhaust device 11 ... Gate valve 12 High-frequency power source 14 F-added SiO ₂ film 15 Al wiring 16 F-added SiO ₂ film 21 Semiconductor substrate 22 BPSG film 23 Al wiring 24 Pure SiO ₂ film 25 F-added SiO ₂ film 26 Pure SiO ₂ film 27 ... Via hole 28 ... Tungsten film 29 ... Al wiring 30 ... Pure SiO ₂ film 31 ... F addition SiO ₂ film 32 ... Pure SiO ₂ film 41 ... Semiconductor substrate 42 ... Substrate support 43 ... Resistance heater 44 ... Cooling Pipe 45 ... Exhaust device 46 ... Nozzle 47 ... High-frequency coil 48 ... High-frequency power source 49 ... High-frequency power source 50 ... F, N-doped SiO ₂ film 51 ... Al wiring 52 ... F, N-doped SiO ₂ film 53 ... Al wiring 54 ... F, N-added SiO ₂ film 60 ... F, B-added SiO ₂ film 61 ... Al wiring 62 ... F, B-added SiO ₂ film 63 ... Al wiring 64 ... F, B-added SiO ₂ film

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/768 H01L 21/321 H01L 21/3205 H01L 21/3213 H01L 21/31

Claims (4)

(57) [Claims] 1. A conductive layer is electrically separated from at least S.
What is claimed is: 1. A semiconductor device comprising an insulating film having a network structure of SiO ₂ , containing i, O and F , having a defect due to O having a dangling bond not involved in bridging of the mesh structure, or having a dangling bond. Defects due to the trapping of electrons or holes by O are centered on the Si bonded to the F.
A semiconductor device characterized by not existing within a region having a radius of 0.39 nm or less . 2. The conductive layers are electrically separated from each other, and at least S
A semiconductor device including an insulating film having a network structure of SiO ₂ containing i, O and F , having dangling bonds that do not participate in crosslinking of the network structure, and having an electronegativity higher than Si. Defects caused by atoms, or defects caused by the atoms having this dangling bond capturing electrons or holes
Has a radius of 0.3 centered on the Si bonded to the F
A semiconductor device which is not present in a region within 9 nm . 3. The conductive layers are electrically separated from each other, and at least S
What is claimed is: 1. A semiconductor device comprising an insulating film having a network structure of SiO ₂ , containing i, O, and F , having a dangling bond that does not participate in crosslinking of the network structure, and is a defect due to an atom that can serve as an electron donor. has a dangling bond not participating in the crosslinking of the network structure, and defects due to atom having a lone pair of electrons or defects due to the atoms having these dangling bonds trapping electrons or holes, wherein F is Before combined
It exists in the area within a radius of 0.39 nm centered on Si.
A semiconductor device characterized by not existing . 4. The semiconductor device according to claim 1, wherein the insulating film contains N or B.