JP2003297821A - Siloxane polymer film on semiconductor substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a siloxane polymer insulation film having high reliability and a low dielectric constant. <P>SOLUTION: The siloxane polymer insulation film has a dielectric constant of 3.1 or lower, and has a -SiR<SB>2</SB>O- repeated structural unit having a concentration of C atoms of 20% of lower. A siloxane polymer has high heat resistance and moisture resistance. The siloxane polymer is formed by directly gasifying a silicon-based hydrocarbon compound expressed by a chemical formula Si<SB>α</SB>O<SB>α-1</SB>R<SB>2α-β+2</SB>(OC<SB>n</SB>H<SB>2n+1</SB>)<SB>β</SB>, where α is an integer of 1 to 3, β is 2, n is an integer of 1 to 3, and R is a C<SB>1-6</SB>hydrocarbon bonded to Si, and then introducing the gasified compound into a reaction chamber of a plasma CVD unit together with an oxidant. The retention time of source gas is extended by reducing the total flow rate of reaction gas, resulting in the formation of the siloxane polymer film of a porous structure having a low dielectric constant. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to semiconductor technology, and more particularly to siloxane polymer insulating films on semiconductor substrates and methods for forming such films using plasma enhanced chemical vapor deposition (CVD) equipment.

[0002]

2. Description of the Related Art Due to the increasing demand for higher integration of semiconductor devices in recent years, multi-layer wiring technology has been receiving attention. The obstacle to high-speed operation of the device in this multilayer wiring structure is
It is the capacitance between the wires. In order to reduce this inter-wiring capacitance, it is necessary to lower the dielectric constant (relative permittivity) of the insulating film.
Therefore, low dielectric constant insulating film materials have been developed.

The conventional silicon oxide film SiO _x is SiH ₄ or
Oxygen as an oxidant is added to silicon material gas such as Si (OC ₂ H ₅ ) _4.
O ₂ or nitric oxide N ₂ O is added, and it is manufactured by heat and plasma energy. Its relative permittivity is 4.0
It is a degree.

On the other hand, an attempt was made to produce a fluorinated amorphous carbon film by the plasma CVD method using C _X F _Y H _Z as a material gas. Its relative permittivity ε is 2.
It is as low as 0 to 2.4.

Attempts have also been made to lower the dielectric constant of the film by utilizing the highly stable nature of the Si-O bond. The silicon-based organic film is produced from the material gas at a low pressure (1 Torr) by the plasma CVD method. The material gas is produced by vaporizing P-TMOS (finyltrimethoxysilane) (chemical formula 1), which is a compound of benzene and silicon, by the bubbling method. This insulating film achieved a low dielectric constant of relative permittivity ε = 3.1.

[0006]

[Chemical 1] In addition, other methods utilize a porous structure created in the membrane. The insulating film is manufactured by a spin-coat method using an inorganic SOG material. The relative permittivity ε of this insulating film is 2.3.

[0007]

However, each of the above approaches has various drawbacks as described below.

First, the fluorinated amorphous carbon film has the drawbacks of low heat resistance (370 ° C.), poor adhesion to silicon-based materials, and low mechanical strength of the film.
If the heat resistance is low, the insulating film may be damaged in a high temperature process of 400 ° C or higher. If the adhesion is poor, there is a risk that the film will peel off. Furthermore, if the mechanical strength of the film is reduced, the wiring material may be damaged.

The oligomer polymerized using the P-TMOS molecule does not form a linear structure such as a siloxane structure in the gas phase because the P-TMOS molecule has _three O-CH ₃ bonds. The oligomer having no linear structure cannot form a porous structure on the silicon substrate, and the density of the deposited film is not reduced. As a result, the dielectric constant of the film is not reduced to the desired degree.

The bubbling method is a method in which vapor of a liquid material obtained by passing a carrier gas such as argon gas through the liquid material is introduced into the reaction chamber together with the carrier gas. This method generally requires a large amount of carrier gas to secure the flow rate of the material gas. As a result, the time for which the material gas stays in the reaction chamber becomes short, and the polymerization reaction does not sufficiently occur in the gas phase.

Further, the SOG insulating film formed by the spin coating method has a problem of uneven coating of the material on the substrate and a problem of the device cost spent on the curing device after the coating process.

[0012]

According to one aspect of the present invention,
Therefore, a high quality siloxane polymer has the chemical formula Si _α
O_α-1R_{2α-β + 2}(OC_nH_{2n + 1})_β(Where α is an integer from 1 to 3,
β is 2, n is an integer from 1 to 3, and R is a bond to Si_1-6Carbonized water
Vaporize silicon-based hydrocarbon compounds (which are
Plasma CVD equipment for vaporized compounds with post-oxidizer
It is formed by introducing it into the reaction chamber. So
The residence time of the source gas reduces the total flow rate of the reaction gas
Porous with extended and thus low dielectric constant
A siloxane polymer film having a structure is formed.

In the above, if the additive gas does not contain an oxidizer but contains a gas such as He, H ₂ , CH _4, etc., k = 2.6-
A low dielectric constant film having a low dielectric constant of 3.1 is obtained. In particular, when the compound of the material gas has two alkoxyl groups and an oxidant is added to the additive gas, the film formation speed is accelerated to improve the productivity, thereby lowering the dielectric constant of k <3.1 at a low cost. It becomes possible to form a low dielectric constant (low-k) film having the same. Further, in the above, by controlling the flow rate of the oxidizing agent, the oxygen concentration in the film is increased without forming an oxide film, the dielectric constant is surprisingly lowered, and the film formation rate is greatly increased. The above effect is prominent when (i) the flow rate of the reaction gas is reduced, (ii) the material gas has two alkoxyl groups, and (iii) the oxidizing gas is added to the additive gas. The resulting siloxane polymer film has a dielectric constant of 3.1 or less, and -SiR ₂ O- repeating structural units with a C atom concentration of 20% or less (ie, the compound is mainly or selectively Is decomposed in the bond between hydrocarbon and oxygen). C
Etching resist (photosensitive resin) when the atomic concentration is low
The selectivity with respect to is improved. Additionally, siloxane polymers have high heat resistance and high humidity resistance on semiconductor substrates. Moreover, this technique can lower the dielectric constant of the film to approximately 2.4, thus expanding the range of applicable devices. Furthermore, according to the present invention, the device manufacturing cost is reduced and the production rate is greatly improved.

In order to summarize the invention and its advantages over the prior art, certain objects and advantages of the invention have been set forth above. Of course, it should be understood that not necessarily all such objects or advantages are achieved in accordance with a particular embodiment of the invention. Thus, for example, one skilled in the art would
The invention is practiced in a manner that achieves or optimizes one or more of the advantages as taught herein, without necessarily achieving the other objectives or advantages as taught or suggested herein. Or know that it can be done.

Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention is a method for forming a siloxane polymer insulating film on a semiconductor substrate by plasma treatment, which method comprises: A step of vaporizing a silicon-based hydrocarbon compound to generate a material gas, wherein the silicon-based hydrocarbon has a chemical formula Si _α O _α-1 R _{2 α -β + 2} (OC _n H _{2n + 1} ) _β (where α is an integer of 1 to 3, β is 2, n is an integer of 1 to 3 and R is Si
A C _1-6 hydrocarbon that binds to), (ii) introducing a material gas into a reaction chamber for plasma CVD processing in which a semiconductor substrate is placed, and (iii) an inert gas And a step of introducing an additional gas consisting of an oxidizing gas, wherein the oxidizing gas is used at a flow rate lower than that of the material gas, and (iv) a semiconductor by activating a plasma polymerization reaction in the reaction chamber. On board-S
and a step of forming a siloxane polymer film having a repeating structural unit of iR ₂ O-.

In the above, when the additive gas comprises an oxidizing gas in an effective amount (for example, 20 to 80% of the material gas by sccm measurement, preferably 40 to 60% of the material gas), the C atom of the siloxane polymer film The concentration is only 20%. The low C atom concentration is very effective for the etching process described below.

Low C concentration and etching treatment The device wiring structure manufacturing process consists of the following steps.
It An insulating film such as a low-k film is formed on the wafer
A resin (etching resist) is formed on the insulating film,
Register the necessary parts using true-sensitization lithography technology
The resist pattern on the wafer
Is formed. After this, ionized CF _Four, Argonga
Emitting ions such as ions perpendicularly to the wafer from above
Formed on the part not covered by the resist by
The wiring shape for removing the removed insulating film and burying Cu
Is formed. In this etching process, the resist
Is also etched at the same time. For this reason, if Regis
If the etching resistance of the
Thicker resists are required to protect. further,
Save as pattern to reduce device nodes
The width of the resist to be applied becomes shorter and
The ratio of the height of the resist is increased. This allows wiring
Processing becomes difficult and resists the etching rate of low-k films
Etching rate and etching selection
It is required to improve the sex.

[0019]

[Table 1] CF ₄ -based etching of low-k films is performed by decomposing Si and C, which make up the chemical structure, into the dissociated gases shown in I to VI above. In a low-k film containing mainly Si, Si is decomposed by changing to a gas such as SiF ₄ due to F existing in the etching gas, and C contained in the film exists in the film. As a result of binding with O, it decomposes by changing into a gas such as CO. At the same time, the resist is etched to some extent while the chemical structure of C is transformed by F into a gas such as CF ₄ . In the case of conventionally used oxide film etching, reaction VII is
Progresses faster and a high etching selectivity is achieved. In the case of low-k film etching, reaction III compared to reaction I
Progress fast enough. However, since the reaction V proceeds as slowly as the reaction I, the high etching selectivity achieved in the oxide film etching cannot be achieved. But,
Since reaction V is caused by oxygen contained in the film, low-k
The film etching is accelerated. Selective etching is effectively achieved when the C atom concentration of the film is 20% or less.

Further, when the C atom concentration of the film is low, not only the etching selectivity but also the etching performance is improved as described below. From a strict technical viewpoint, it is necessary to consider the plasma state for the etching reaction. However, since the above reaction model is very complicated, a stoichiometric model of a simple reaction is considered here. Membrane structures are analyzed using XPS, a widely used method for accurate analysis. H is not analyzed by this method, and H
Decomposes into gas itself. Therefore, reactions of elements other than H are discussed below.

If oxygen is not added, the etching reaction formula of the SiOCH low-k film not covered by the resist is as follows. When the ratio of O contained in the Si _x O _y C _z + mCF ₄ → xSiF ₄ + aCO + bC film is small, a phenomenon occurs in which C is not vaporized enough to stop etching and accumulates. Therefore, an experiment is conducted to speed up the etching rate by vaporizing carbon contained in the film into CO or CO ₂ by adding a small amount of oxygen to the etching gas. The reaction formula is as follows. Si _x O _y C _z + xCF ₄ + nO ₂ → xSiF ₄ + (x + z) CO In order to carry out the above reaction formula, stoichiometrically n = (x + zy)
It is necessary to add / 2 oxygen O ₂ . Deformatively, in the case of a model in which C is vaporized to CO ₂ , the chemical reaction formula is as follows. Si _x O _y C _z + xCF ₄ + nO ₂ → xSiF ₄ + (x + z) CO _{2 In} order to carry out the above reaction formula, it is necessary to add n = x + zy / 2 oxygen O ₂ . However, it was formed as a low dielectric constant film without adding an oxidizer to the added gas, and the SiOCH
The -k film contains 20% or more C. The composition of the low-k film formed using the previous technology J-039 (Example of film formation in comparative experiment) is Si:
It is C: O = 33: 22: 45 (%). In this case, x = 0.33, y = 0.45 and z = 0.22. In the model where C decomposes into CO, n = 0.1, and in the model where C decomposes into CO ₂ , n = 0.325. In other words, CF ₄ : 0.33 mol F
It can be seen that it is necessary to add approximately 0.1 mol to 0.33 mol of oxygen O ₂ to the gas.

Residence Time and Gas Flow Rate The residence time of the reaction gas is determined based on the volume of the reaction chamber, the pressure adapted to the reaction and the total flow rate of the reaction gas. The reaction pressure is usually in the range of 1 to 10 Torr, but is preferably 3 to 7 Torr in order to maintain a stable plasma. This reaction pressure is relatively high in order to prolong the residence time of the reaction gas. The total flow rate of the reaction gas is important for reducing the dielectric constant of the produced film. It is not necessary to control the ratio of source gas to additive gas. Generally, the longer the residence time, the lower the dielectric constant. The flow rate of the material gas required for film formation depends on the desired growth rate and the area of the substrate on which the film is formed. For example, it is expected that at least 50 sccm of material gas should be included in the reaction gas to form a film on the substrate (radius r = 100 mm) at a growth rate of 300 nm / min. It is approximately 1.6 × 10 ² sccm per surface area (m ² ) of the substrate. The total flow rate is defined by the residence time (Rt). When Rt is defined as described below, the preferred range of Rt is 100 msec ≤ R
t, more preferably 165 msec ≦ Rt, even more preferably 200 msec
≦ Rt ≦ 5 sec. In conventional plasma TEOS, Rt is generally in the range of 10-30 msec. Rt [s] = 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F where Pr: Reaction chamber pressure (Pa) Ps: Standard atmospheric pressure (Pa) Tr: Average temperature of reaction gas (K) Ts: Standard temperature (K) r _w : Radius of silicon substrate (m) d: Distance between silicon substrate and upper electrode (m) F: Total flow rate of reaction gas (sccm) In the above, the residence time is It refers to the average time interval during which gas molecules stay in the reaction chamber. Residence time Rt is Rt = αV
/ S, where V is the volume of the chamber (cc), S is the volume of the reaction gas (cc / s), and α is the shape of the reaction chamber and the positional relationship between the gas inlet and outlet. Is a coefficient determined by. The reaction space in the reaction chamber is the substrate surface area
It is defined by (πr ² ) and the space between the upper and lower electrodes. Considering the gas flow rate through the reaction space,
α can be estimated to be 1/2. In the above formula, α is 1/2.

Material gas and additive gas In the present invention, the general formula Si _α O _β C _x H _y (α, β, x and y
Is a chemical formula Si _α O _α-1 R _{2 α -β + 2} (OC _n H _{2n + 1} ) _β (where α is an integer of 1 to 3, β Is 2, n is an integer of 1 to 3 and R is a C _1-6 hydrocarbon bonded to Si). That is, a preferred compound is at least one Si-O bond,
It has two OC _n H _{2n + 1} bonds and two hydrocarbon radicals bonded to silicon. In the above examples, the alkoxy present in the silicon-based hydrocarbon has 1 to 3 carbon atoms. In another embodiment, the hydrocarbon present in the silicon-based hydrocarbon compound has 1 to 6 carbon atoms (n = 1-6). In another embodiment, the silicon-based hydrocarbon compound has 1 to 3 silicon atoms. In yet another embodiment, the silicon-based hydrocarbon compound has 1 to 2 silicon atoms (α = 1 or 2). More specifically, the silicon-based hydrocarbon contains at least one gas species of the compound represented by Chemical Formula 2 below.

[0024]

[Chemical 2] Here, R1 and R2 is one of _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H _5, m and n are any integers.

In addition to those gas species described above, the silicon-based hydrocarbon compound contains at least one gas species of the compounds represented by the following chemical formula 3.

[0026]

[Chemical 3] Here, R1, R2, R3 and R4 are one of _{CH 3, C 2 H 3,} C 2 H 5, C 3 H 7 and C ₆ H _5, m and n are any integers.

It should also be noted that the silicon-based hydrocarbon compound is any combination of these compounds and mixtures.

According to another aspect of the present invention, an insulating film is formed on a substrate and the film is formed by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Chemical Formula 2. Polymerized.

Additionally, an insulating film is formed on the substrate and the film is polymerized by plasma energy in a plasma CVD apparatus using a material gas containing a silicon-based hydrocarbon compound represented by Chemical Formula 3.

According to a further aspect of the invention, the material for forming the insulating film is provided in the gas phase near the substrate and processed in a plasma CVD apparatus to form the insulating film on the substrate by a chemical reaction, In addition, the material has the chemical formula 2
Represented by

Additionally, the material for forming the insulating film is supplied in the vapor phase near the substrate and processed in a plasma CVD apparatus to form an insulating film on the substrate by a chemical reaction, and the material is It is represented by Chemical Formula 3.

Additive gases usable in the present invention are, for example, argon gas and helium gas. In the examples, primarily argon is used to stabilize the plasma, while helium is used to improve plasma uniformity and insulating film thickness uniformity.

In the above-described method, the first step of direct vaporization is a method in which the liquid material with a controlled flow rate is immediately vaporized in a preheated vaporizer. This direct vaporization method does not require a carrier gas such as argon to obtain the specified amount of source gas. This point is very different from the bubbling method. Therefore, a large amount of argon gas or helium gas is no longer required, which reduces the total gas flow rate of the reaction gas and prolongs the time the material gas stays in the plasma. As a result, a sufficient polymerization reaction takes place in the gas phase, resulting in the formation of a linear polymer and a membrane having a porous structure.

In FIG. 1, the inert gas supplied through the gas supply port 14 pushes the liquid reaction material 18, which is a silicon-based hydrocarbon compound, through the line 13 to the control valve 8. The control valve 8 controls the flow rate of the liquid reaction material 18 by means of the flow controller 7, so that it does not exceed a predetermined volume. Reduced silicon hydrocarbon compounds
18 goes to the vaporizer 17 and is vaporized by the above-mentioned direct vaporization method. Argon and helium are supplied through the air supply ports 15 and 16, respectively, and the valve 8 controls the flow rates of these gases. The reaction gas, which is a mixture of the material gas and the additive gas, is then supplied to the gas introduction port 5 of the plasma CVD apparatus 1. The space between the gas diffusion plate 10 and the semiconductor substrate 4 arranged in the reaction chamber 6 which has been exhausted is preferably 1
Charged with high frequency RF voltage of 3.4MHz and 430kHz, the space acts as a plasma field. The susceptor 3 continuously heats the semiconductor substrate 4 with the heater 2, and preferably maintains the substrate 4 at a predetermined temperature of 350 to 450 ° C. The reaction gas supplied through the pores of the gas diffusion plate 10 remains in the plasma field near the surface of the semiconductor substrate 4 for a predetermined time.

If the residence time is short, the linear polymer does not grow sufficiently, so that the film deposited on the substrate does not form a porous structure. Since the residence time is inversely proportional to the flow rate of the reaction gas, a decrease in the flow rate of the reaction gas extends the residence time.

By reducing the flow rate of the additive gas, the total flow rate of the reaction gas can be extremely reduced. As a result, the residence time of the reaction gas is extended, and as a result, the linear polymer is sufficiently grown, and subsequently the insulating film having the porous structure is formed.

To control the reaction in the gas phase, it is useful to add small amounts of inert gases, oxidants or reducing agents to the reaction chamber. Helium (He) and Argon (A
r) is an inert gas with different ionization energies of 24.56 eV and 15.76 eV respectively. Therefore, the reaction of the material gas in the gas phase is controlled by adding either or both of He and Ar in a predetermined amount in combination. The molecules of the reaction gas undergo polymerization in the gas phase to form an oligomer. The oligomer is expected to have an O: Si ratio of 1: 1. However, as the oligomer forms a film on the substrate, the oligomer undergoes further polymerization to produce a higher oxygen ratio. The ratio varies depending on the dielectric constant or other properties of the film formed on the substrate (eg, in Example 5 below, the ratio was 3: 2).

Residual oxygen extracted from the material gas and not taken into the film is separated from the material compound and floats in the plasma. The ratio of Si: O in the material gas changes depending on the compound. For example, in the above Chemical Formulas 2 and 3, O: Si
Ratios are 2: 1 and 1: 1 respectively. If high ratio of O: Si
If a source gas with (eg, 2/1 or more) is used, the amount of oxygen suspended in the plasma will increase. When the amount of oxygen increases, the organic groups necessary for forming a film by directly bonding to Si are oxidized, and as a result, the film is likely to deteriorate. In the above, adding reducing agents such as H ₂ and CH ₄ to the reaction chamber reduces the oxygen partial pressure in the plasma, thereby preventing the above oxidation of organic groups. In contrast, the O: Si ratio is low (eg 2/1
Or less), it is necessary to supply oxygen for forming a film by adding an oxidizing agent such as N ₂ O and O ₂ . The appropriate amount of the reducing agent or the oxidizing agent is previously evaluated based on preliminary experiments in which the composition of the formed film is analyzed by FT-IR or XRS, and its dielectric constant is also analyzed. Therefore, by selecting the appropriate type of additive gas such as He, Ar, reducing agent and oxidizing agent, and by controlling the amount of each gas to be added,
A membrane with the desired quality is produced.

By controlling the flow rate of the oxidizer within the range of the flow rate of the material gas or less, the oxygen concentration in the film is increased without forming an oxide film structure, the dielectric constant is surprisingly lowered, and the growth rate is further increased. Greatly increased. The above effect is
This is particularly noticeable when (i) the flow rate of the reaction gas is reduced, (ii) the material gas has two alkoxyl groups, and (iii) the oxidizing gas is added to the additive gas. The resulting siloxane polymer film has a dielectric constant of 3.1 or less, 2
It has a -SiR ₂ O- repeating structural unit with a C atom concentration of 0% or less (ie, the compound is mainly or selectively decomposed at the bond between the hydrocarbon and oxygen).

Polymer Structure In this method, the source gas is at least one Si
A silicon-based hydrocarbon compound containing an -O bond, at most two OC _n H _{2n + 1} bonds and at least two hydrocarbon radicals bonded to silicon. Further, this material gas is vaporized by the direct vaporization method. The method produces an insulating film having a low dielectric constant, high heat resistance and high moisture resistance.

More specifically, the material gas vaporized by the direct vaporization method can stay in the plasma for a sufficiently long time. As a result, a linear polymer is formed,
As a result, a linear polymer having a basic structure (Formula 4) (where n is 2 or more) is formed in the gas phase. Then, the polymer is deposited on the semiconductor substrate to form an insulating film having a porous structure.

[0042]

[Chemical 4] Where X1 and X2 are O _n C _m H _p , n is 0 or 1, m and
p is an integer including zero.

The insulating film of the present invention has relatively high stability because its basic structure has Si—O bond having high bond energy. Also, its dielectric constant is low because it has a porous structure. Furthermore, the basic structure (-Si-O-) _n has dangling bonds terminated by hydrophobic hydrocarbon radicals on both sides, and this property provides moisture resistance. Furthermore, the bond between the hydrocarbon radical and silicon is generally stable. For example, both the Si—CH ₃ bond with a methyl radical and the Si—C ₆ H ₅ bond with a benzene have a decomposition temperature of 500 ° C. or higher. 450 ° C for the above semiconductor manufacturing
Due to the need for thermal stability at these temperatures, the properties of the film are advantageous for semiconductor manufacturing. In the example,
The temperature for plasma polymerization is approximately θ ± 50 ° C, where θ
Is the heat resistant temperature required for the film.

In particular, in the examples, the siloxane polymer film formed on the semiconductor substrate by the method described above is
Alternatively, it has a dielectric constant of less than that, has a -SiR ₂ O-repeating structural unit, and has a chemical formula Si _α O _α-1 R _{2 α -β + 2} (OC _n H
_{2n + 1} ) _β (where α is an integer from 1 to 3, β is 2, n is an integer from 1 to 3 and R is a C _1-6 hydrocarbon bonded to Si) It has a C atom concentration of 20% or less formed by plasma polymerization reaction. In another embodiment, the siloxane polymer film has a dielectric constant of 2.7. In yet another embodiment, the siloxane polymer film has C ₁ hydrocarbon R in the repeating structural unit.

Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments presented below.

Outline of Example Structure FIG. 1 schematically shows a plasma CVD apparatus usable in the present invention. Equipment is reaction gas supply device 12 and plasma CV
Consists of D device 1. The reaction gas supply device 12 comprises several lines 13 and a control valve 8 and gas supply ports 14, 15, 16 arranged on the line 13. A flow rate controller 7 is connected to each control valve 8 to control the material gas to a predetermined flow rate. A vaporizer 17 for directly vaporizing a liquid is connected to a container for containing the liquid reaction material 18. The plasma CVD apparatus 1 includes a reaction chamber 6, a gas inlet 5, a susceptor 3 and a heater 2. The circular gas diffusion plate 10 is arranged immediately below the gas inlet. A large number of pores are provided on the bottom surface of the circular gas diffusion plate 10, and the reaction gas is jetted toward the semiconductor substrate 4 from there. An exhaust port 11 is provided at the bottom of the reaction chamber 6. The inside of the reaction chamber 6 is evacuated by connecting the exhaust port 11 to an external vacuum pump (not shown). The susceptor 3 is arranged so as to face the gas diffusion plate 10 in parallel. The susceptor 3 heats and holds the semiconductor substrate 4 placed on its surface through the heater 2. Gas inlet 5
Is electrically insulated from the reaction chamber 6 and connected to an external high frequency power supply 9. Here, the susceptor 3 is the high frequency power source 9
May be connected to. Thus, the gas diffusion plate 10 and the susceptor
3 functions as a high frequency electrode and generates a plasma reaction region near the surface of the semiconductor substrate 4.

A method for forming an insulating film on a semiconductor substrate using the plasma CVD apparatus according to the present invention is described in general formula Si
a step of vaporizing a silicon-based hydrocarbon compound represented by _α O _β C _X H _Y (where α, β, x, and y are integers) by a direct vaporization method and introducing it into a reaction chamber of a plasma CVD apparatus; A step of introducing an additive gas having a substantially reduced flow rate into the reaction chamber, and a mixed gas of a silicon-based hydrocarbon compound gas as a material gas and an additive gas as a reaction gas,
And a step of forming an insulating film on the semiconductor substrate by a plasma polymerization reaction. It is characterized in that the total flow rate of the reaction gas is substantially reduced by reducing the flow rate of the additive gas. This feature is explained in more detail below.

Other technologies Oxide film₂And N₂Oxidizing gas such as O is used for organosilicon SiR
_x(OR)_y(Where R is C _nH_m, X, y are random numbers)
Formed by using the usual plasma CVD method.
There are some examples. However, the film formed at this time is about
An oxide film with a dielectric constant of 4 and a low dielectric constant film of the next generation
Can not be used.

Furthermore, an example was reported in which a low dielectric constant film having a dielectric constant of 2.7 was formed on SiH (CH ₃ ) ₃ by using an oxidizing gas such as N ₂ O. The film formed in this case is a SiCOH film having a high C concentration of 20% or more.

[0050]

[Example] Device configuration Figure 2 shows a parallel plate type CVD system.
It A pair of electrically conductive plate electrodes facing each other and
They are placed in parallel in the reaction chamber, with a 27 MHz RF
These pairs by applying force and grounding the other
Plasma is excited between the electrodes. Temperature adjustment mechanism is lower
Mounted on the stage side, temperature is nearly 400 ° C (752 ° F)
Maintained at. DM-DMOS (Dimethyldimethoxysilane) S
i (CH₃)₂(OCH ₃)₂And inert gases such as He and Ar and
Additionally O₂And N₂Oxidizing gas such as O is mixed and
Used as a reaction gas. Each gas is supplied from 21 to 23
And flow rate adjusters 24 to 26 to adjust to the given flow rate,
These are mixed and used as reaction gas at the top of the upper electrode.
Introduced into mouth 27. 500 to 10,000 pores of approximately φ0.5 mm
(3,000 sub-modes in the mode for carrying out the invention
Holes are formed) are introduced into the upper electrode
Reaction gas flows through these pores into the reaction chamber.
Run in. The reaction space is evacuated by a vacuum pump,
It is maintained at a predetermined constant pressure of 600Pa.

Long-term residence plasma C using DM-DMOS as a film forming reaction material gas
A film was formed by VD under the following conditions. Oxygen was added to the reaction gas at a flow rate equal to or lower than that of the material gas DM-DMOS. RF power: 1500W (using a frequency of 27MHz) (preferably 500
Substrate temperature: 400 ° C. (preferably 300 to 600 ° C.) reaction pressure: 650 Pa (preferably 400 to 1000 Pa) Residence time (Rt) is defined by the following formula. Rt [s] = 9.42 × 10 ⁷ (Pr · Ts / Ps · Tr) r _w ² d / F In this formula, each abbreviation represents the following parameter. Pr: Reaction chamber pressure (Pa) Ps: Standard atmospheric pressure (Pa) Tr: Average temperature of reaction gas (K) Ts: Standard temperature (K) r _w : Radius of silicon substrate (m) d: Silicon substrate and upper electrode Distance (m) F: Total flow rate of reaction gas (sccm) Each parameter was fixed to the following value. Only the flow rate was varied to find the relationship between flow rate and dielectric constant. Pr ＝ 6.50 × 10 ² (Pa) Ps = 1.01 × 10 ⁵ (Pa) Tr ＝ 273 + 400 = 673 (K) Ts ＝ 273 (K) r _w ＝ 0.1 (m) d ＝ 0.014 (m) Table 1 shows It is a summary of the experimental results of the comparative example and the example of the present invention.

[0052]

[Table 2] Experimental Results Example 1 140 sccm of DM-DMOS as a source gas, 70 sccm of O ₂ and 30 sccm of He as an additive gas were mixed and introduced into the reaction chamber as a reaction gas. The pressure inside the reaction chamber was evacuated by a vacuum pump from time to time and maintained at 650 Pa. RF power of 27 MHz at 1500 W was applied to the top electrode. The temperature of the lower stage was adjusted to a constant temperature of 400 ° C (752 ° F). Under these conditions, the film was formed at a rate of 500 nm / min and the dielectric constant measured by applying a voltage of 1 MHz to the formed film was 2.70. The film structure measured by XPS was Si: C: O = 33: 22: 45 (%).

The results of the above experiments are summarized in the table below.

[0054]

[Table 3]

[0055]

The present invention enables formation of a low dielectric constant film by using the plasma CVD method. By using this low dielectric constant film as an insulating film for a highly integrated semiconductor device, the delay caused by the inter-wiring capacitance is reduced and the operating speed of the semiconductor device is substantially increased. For example, as the device node size decreases, as shown in the table below,
A lower dielectric constant (low-k) is required for the interlayer insulating film used in the device.

[0056] For the low-k film having a dielectric constant of approximately 2.7, many film forming methods such as the CVD method and the coating method have been proposed, and in recent years, it has become possible to form a high-quality low-k film. 0.10
Attempts have been made to apply the method to mass-produced devices with ~ 0.13 μm device nodes. For next generation high speed devices, lower low-k films with a dielectric constant of approximately k = 2.5 or lower are currently required. The present invention provides high quality membranes required by the industry.

Those skilled in the art will recognize that various modifications can be made without departing from the spirit of the invention. Therefore, it should be understood that the form of the present invention is illustrative only and does not limit aspects of the invention.

[Brief description of drawings]

FIG. 1 is a plasma CVD used for manufacturing an insulating film.
1 is a schematic view of a device.

FIG. 2 is a schematic diagram of a plasma CVD apparatus used in an experiment.

[Explanation of symbols]

1 Plasma CVD equipment 2 heater 3 susceptor 4 Semiconductor substrate 5 Gas inlet 6 Reaction chamber 7 Flow controller 8 Control valve 9 High frequency power supply 10 gas diffusion plate 11 Exhaust port 12 Reaction gas supply device 13 lines 14 Gas air supply port 15 gas supply port 16 gas supply port 17 Vaporizer 18 Liquid reaction material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshinori Morisada             6-23-1, Nagayama, Tama-shi, Tokyo Japan             -Inside SMM Co., Ltd. (72) Inventor Satoshi Takahashi             6-23-1, Nagayama, Tama-shi, Tokyo Japan             -Inside SMM Co., Ltd. F term (reference) 5F033 RR23 RR29 SS01 SS15 XX24                 5F058 AA10 AC03 AF02

Claims (14)

[Claims] 1. A white substrate formed on a semiconductor substrate by plasma treatment.
A method for forming a xane polymer insulating film, comprising: Silicon to produce material gas for siloxane polymers
A step of vaporizing a hydrocarbon-based compound, the method comprising:
Hydrocarbons have the chemical formula Si_αO_α-1R_{2α-β + 2}(OC_nH_{2n + 1})_β
(Where α is an integer from 1 to 3, β is 2 and n is an integer from 1 to 3 and R
Is C bonded to Si _1-6(Which is a hydrocarbon)
Process, Reaction chamber for plasma CVD process with semiconductor substrate
Introducing a material gas into the chamber, A process for introducing an additive gas consisting of an inert gas and an oxidizing gas.
However, the oxidizing gas is used in a smaller amount than the source gas.
The process used By causing a plasma polymerization reaction in the reaction chamber
On a semiconductor substrate-SiR ₂O-having a repeating structural unit
Forming a loxane polymer film. 2. A method according to claim 1, wherein the additive gas comprises an oxidizing gas in an amount effective to bring the C atom concentration of the siloxane polymer film to at most 20%. 3. The method according to claim 1, wherein in the plasma polymerization reaction, the flow rate of the reaction gas is controlled so as to extend the residence time Rt of the reaction gas in the reaction chamber so that 100 msec ≦ Rt. Raised, Rt is Rt [s] = 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F where Pr: Reaction chamber pressure (Pa) Ps: Standard atmospheric pressure (Pa) Tr : Average temperature of reaction gas (K) Ts: Standard temperature (K) r _w : Radius of silicon substrate (m) d: Distance between silicon substrate and upper electrode (m) F: Total flow rate of reaction gas (sccm) The method as defined. 4. The method according to claim 1, wherein the residence time is determined by correlating the dielectric constant with the residence time. 5. The method according to claim 1, wherein the additive gas comprises at least argon (Ar) or helium (He). 6. The method according to claim 1, wherein the flow rate of the reaction gas is controlled so that the relative dielectric constant of the siloxane polymer film is 3.10. 7. The method of claim 1, wherein Rt is at least 165 msec. 8. The method according to claim 1, wherein the alkoxy present in the silicon-based hydrocarbon has 1 to 3 carbon atoms. 9. The method according to claim 1, wherein the hydrocarbon present in the silicon-containing hydrocarbon compound has 1 to 6 carbon atoms (n = 1 to 6). 10. The method of claim 1, wherein the silicon-based hydrocarbon compound has 1 to 3 silicon atoms. 11. The method according to claim 1, wherein the silicon-based hydrocarbon compound is 1 or 2 silicon atoms.
The method of having (α = 1 or 2). 12. A siloxane polymer insulating film formed on a semiconductor substrate by the method of claim 1, having a dielectric constant of 3.1 or less, and having -SiR ₂ O-repeating structural units, And the chemical formula Si _α O _α-1 R _{2 α- β + 2} (OC _n H _{2n + 1} ) _β
(Where α is an integer from 1 to 3, β is 2 and n is an integer from 1 to 3 and R
Is a C _1-6 hydrocarbon bonded to Si) formed by a plasma polymerization reaction from a silicon-based hydrocarbon having 20
A siloxane polymer insulating film having a C atom concentration of 10% or less. 13. The siloxane polymer insulating film according to claim 12, which has a dielectric constant of 2.7 or less. 14. The siloxane polymer insulating film according to claim 12, wherein the R in the repeating structural unit is C ₁ hydrocarbon.