JP2004228581A - Insulation film on semiconductor substrate and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an improved insulation film which has a low dielectric constant and better film quality. <P>SOLUTION: The insulation film is formed on a semiconductor substrate by vaporizing a silicon-containing hydrocarbon compound to provide a source gas, introducing a reaction gas composed of the source gas and an additive gas such as an inert gas and oxidizing gas to a reaction space of a plasma CVD apparatus, and depositing a siloxan polymer film by plasma polymerization at a temperature of -50-100°C. The residence time of the reaction gas in the reaction space is lengthened by reducing the total flow of the reaction gas in such a way as to form the siloxan polymer film with a low dielectric constant such as 2.5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  This application is a continuation-in-part of US Patent Application No. 10 / 288,641 filed on November 5, 2002, which is a continuation-in-part of US Patent Application No. 09 / 827,616 filed on April 6, 2001. (I) claimed priority based on Japanese Patent Application No. 10-37929 filed in Japan on February 5, 1998 and was filed on February 2, 1999, now abandoned. US patent application Ser. No. 09 / 243,156, (ii) US patent application Ser. No. 09 / 326,847 (currently US Pat. No. 6,352,945) filed on June 7, 1999, (iii) June 7, 1999. Filed US patent application Ser. No. 09 / 326,848 (currently US Pat. No. 6,383,955) and (iv) US patent application Ser. No. 09 / 691,376 filed Oct. 18, 2000 (currently US Pat. No. 6,432,846). No.). All of which are hereby incorporated by reference. This application also claims priority from US Provisional Patent Application No. 60 / 442,731, filed Jan. 24, 2003, which is incorporated herein by reference. This application claims priority under all 35U.S.C.119 and 120 under the above.

  The present invention relates generally to semiconductor technology, and more particularly to a silicon polymer insulating film on a semiconductor substrate and a method for forming a film using a plasma CVD (chemical vapor deposition) apparatus.

  In recent years, multilayer wiring technology has attracted much attention due to the increasing demand for large-scale integration of semiconductor devices. However, in these multilayer structures, the capacitance between individual wirings hinders high-speed operation. In order to reduce the capacitance, it is necessary to reduce the dielectric constant of the insulating film. Therefore, various materials having a relatively low dielectric constant have been developed for insulating films.

  The conventional silicon oxide film SiOx is manufactured by a method in which oxygen O2 or nitrogen oxide N2O is added as an oxidant to a silicon source gas such as SiH4 or Si (OC2H5) 4 and then processed by heat or plasma energy. It was. Its relative dielectric constant is about 4.0.

  A fluorinated amorphous carbon film was also produced from CxFyHz as a source gas by plasma CVD. Its relative dielectric constant ε is as low as 2.0 to 2.4.

  Another way to reduce the dielectric constant of the insulating film was done by using good stability of Si-O bond. A silicon-containing organic film is manufactured from a source gas under a low pressure (1 Torr) by a plasma CVD method. The source gas is made of P-TMOS (Phenyl Trimethoxysilane, Chemical Formula 1), which is a compound of benzene and silicon and is vaporized by a bubbling method. The relative dielectric constant ε of this film is as low as 3.1.

さらに他の方法は膜中に作られた多孔構造を使用する。絶縁膜はスピンコート法によって無機SOG材料から製造される。当該膜の比誘電率εは２.３と低い。

Yet another method uses a porous structure made in the membrane. The insulating film is manufactured from an inorganic SOG material by spin coating. The relative dielectric constant ε of the film is as low as 2.3.

  However, the above approach has various drawbacks as described below.

  First, the fluorinated amorphous carbon film has lower thermal stability (370 ° C.), poor adhesion with silicon-containing materials, and lower mechanical strength. Lower thermal stability results in damage at high temperatures exceeding 400 ° C. The film easily peels off due to poor adhesion. Lower mechanical strength also puts wiring materials at risk.

  Oligomers polymerized using P-TMOS molecules do not form a linear structure like a siloxane structure in the gas phase because the P-TMOS molecules have three O-CH3 bonds. An oligomer that does not have a linear structure cannot form a porous structure on a silicon substrate. That is, the density of the deposited film does not decrease. As a result, the dielectric constant of the film cannot be reduced to the desired degree.

  In this regard, the bubbling method refers to a method in which vapor of a liquid material obtained by passing a carrier gas such as argon gas through the material is introduced into the reaction chamber together with the carrier gas. In general, this method requires a large amount of carrier gas to flow the source gas. As a result, the source gas cannot remain in the reaction chamber for a length of time sufficient to cause polymerization in the gas phase.

  Further, the SOG insulating film of the spin-coat method has a problem that the material is not uniformly applied on the silicon substrate and another problem that the curing apparatus after the coating process is expensive.

  Accordingly, it is a primary object of the present invention to provide a method for forming an improved insulating film.

  Another object of the present invention is to provide an insulating film having a low relative dielectric constant and excellent film quality.

  Still another object of the present invention is to provide a method for easily forming an insulating film having a low dielectric constant without requiring an expensive apparatus.

One embodiment of the present invention relates to a method for forming an insulating film on a semiconductor substrate using a plasma CVD apparatus including a reaction chamber, and the method includes a general formula Si _α O _β C _x H _y (α, β , X and y are integers) and directly vaporize the silicon-containing hydrocarbon compound, and then introduce it into the reaction chamber of the plasma CVD apparatus, and introduce an additive gas into the reaction chamber as necessary. And a step of forming an insulating film on the semiconductor substrate by a plasma polymerization reaction.

  In particular, the present invention includes, but is not limited to, the following examples.

The method includes (a) vaporizing a silicon-containing hydrocarbon compound to provide a source gas, (b) introducing a source gas into a reaction space for plasma CVD processing where a semiconductor substrate is disposed, and ( c) optionally introducing an additive gas selected from the group consisting of an inert gas, an oxidizing gas and a plasma stabilizing gas, wherein the source gas and the additive gas constitute a reactive gas; (d) a step of forming an insulating film on the semiconductor substrate by activating the plasma polymerization reaction in the reaction space at a temperature of about −50 ° C. to about 100 ° C., wherein the plasma polymerization reaction is performed in the reaction space. The reaction gas is activated while controlling the flow rate of the reaction gas so as to extend the residence time Rt of the reaction gas (here, 100 msec ≦ Rt),
Rt [s] ＝ 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F
here,
Pr: Reaction space pressure (Pa)
Ps: Standard atmospheric pressure (Pa)
Tr: Average reaction temperature (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 reactive gas (sccm)
And the process.

  In accordance with the present invention, a low dielectric constant silicon polymer film having a microporous structure is produced. Specifically, the dielectric constant of the insulating film is about 2.5 or less. In the present invention, the reaction temperature is low and the residence time is extended. Therefore, the reaction on the substrate surface does not proceed quickly, and the polymer or oligomer formed in the gas phase in the reaction space accumulates on the substrate surface without further reaction, so that the polymer or oligomer structure accumulates on the surface. It remains as it was. As a result, a polymer or oligomer having a structure close to an ideal siloxane structure (hereinafter simply referred to as a polymer) accumulates, thereby forming a film having a low dielectric constant of about 2.5 or less on the substrate. Is done.

  In order to remove moisture and improve mechanical strength, the method further comprises annealing the insulating film. In an embodiment, the annealing process is performed at approximately 300 ° C. to 450 ° C. by irradiating the insulating film with ultraviolet light or electron beam, or by using a heater under reduced pressure, whereby a film having excellent film quality is obtained. It is formed.

  To summarize the advantages of the invention and the prior art, the objects and advantages of the invention have been described. Of course, it is to be understood that not all of the objects or advantages are achieved according to every particular embodiment of the invention. Thus, for example, the invention is in a manner that achieves or optimizes one set of advantages or advantages taught herein without necessarily achieving other objects or advantages as taught or suggested herein. Those skilled in the art are aware that it can be implemented or implemented.

  Other aspects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments.

In an embodiment of the present invention, a method includes (a) vaporizing a silicon-containing hydrocarbon compound to provide a source gas, and (b) a source gas into a reaction space for plasma CVD processing where a semiconductor substrate is disposed. And (c) optionally introducing an additive gas selected from the group consisting of a carrier gas, an oxidizing gas and a plasma stabilizing gas, wherein the source gas and the additive gas constitute a reactive gas And (d) forming an insulating film on the semiconductor substrate by activating the plasma polymerization reaction at a temperature of about −50 ° C. to about 100 ° C. in the reaction space, The reaction is activated while controlling the flow rate of the reaction gas so as to extend the residence time Rt of the reaction gas in the reaction space (here, 100 msec ≦ Rt),
Rt [s] ＝ 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F
here,
Pr: Reaction space pressure (Pa)
Ps: Standard atmospheric pressure (Pa)
Tr: Average reaction temperature (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 reactive gas (sccm)
And the process.

  In the above, the reaction temperature is -50 ° C, -40 ° C, -30 ° C, -20 ° C, -10 ° C, 0 ° C, 20 ° C, 40 ° C, 60 ° C, 80 ° C and 100 ° C, and any of these. Inclusive range is included. Preferably, the temperature is about -10 ° C to about 50 ° C.

  The additive gas is used for various purposes. The carrier gas is used to carry the source gas or control the source gas reaction (with different excitation energies). In an embodiment, an inert gas is used and is selected from the group consisting of Ar, Kr, Ne, N2 and He. The carrier gas has a flow rate of 0% to 300% of the flow rate of the source gas (50%, 100%, 150%, 200% and 250%, and a range including any of these, preferably 200% or less). Supplied.

  The oxidizing gas is used to oxidize the source gas or supply oxygen to the source gas. In an embodiment, the oxidizing gas is selected from the group consisting of O2, NO, CO2, O3, H2O and N2O. Oxidizing gas at a flow rate of 0% to 300% of source gas flow rate (50%, 100%, 150%, 200% and 250%, and ranges including any of these, preferably 200% or less) Supplied.

The plasma stabilizing gas is used to stabilize the plasma or promote the polymerization or oligomerization of the source gas. In an example, the plasma stabilizing gas was C _1-4 alkanol such as ethylene glycol, 1,2-propanediol and isopropyl alcohol, C _2-4 ether such as diethyl ether, 1,4-cyclohexanediol (bp150 C _4-12 aromatic hydrocarbon and C _4-12 fat containing 1,4-cyclohexanedimethanol (bp 283 ° C.) and 1,3-cyclopentanediol (80-85 ° C./0.1 Torr) Cyclic hydrocarbons, C _4-12 alicyclic hydrocarbon unsaturated compounds such as 1,2,4-trivinylcyclohexane (bp 85-88 ° C./20 mm), and cyclic aldehydes (CH 2 O) n, 3 ≦ n ≦ A group consisting of 6 is selected. The plasma stabilizing gas is 0% to 1000% of the flow rate of the source gas (50%, 100%, 200%, 300%, 400%, 500%, 600%, 700%, 800% and 900%, and any of these) In a range including the above, preferably 500% or less).

In addition, compounds having multiple reactive groups can also be used as plasma stabilizing gas, including but not limited to ethylene glycol vinyl ether H2C = CHOCH2OH (bp 143 ° C.), ethylene glycol divinyl ether H2C = CHOCH2CH2OCH = CH2 (bp 125-127 ° C.), and C _3-20 ether such as 1,4-cyclohexanedimethanol divinyl ether (H 2 C═C (OH) —CH 2) 2 (CH 2) 6 (bp 126 ° C./14 mm), and 1- Contains C _5-12 cycloalkanol vinyl compounds such as vinylcyclohexanol (bp 74 ° C./19 mm).

  The residence time Rt includes 100 msec, 150 msec, 200 msec, 250 msec, 300 msec, 350 msec, 400 msec, 450 msec, and 500 msec and a range including any of these. Preferably, Rt is at least 200 msec.

  The RF power applied to the reaction space has a high frequency (2 MHz or higher) and a power of 30 W to 3000 W (100 W, 500 W, 1000 W and 2000 W, and ranges including any of these). The high frequency RF power is low frequency RF power (such as 400kHz) with 0% to 50% intensity (5%, 10%, 20%, 30% and 40%, and any range including them) of it. 2MHz or less).

  Annealing is performed under reduced pressure (eg, in an evacuated chamber or vacuum) at a temperature of about 300 ° C. to about 450 ° C. to remove moisture from the insulating film and increase its mechanical strength. As any suitable heat transfer means, for example, means for radiating the insulating film with ultraviolet rays, infrared rays, electron beams, plasma (inert gas and / or reducing gas such as H2 or NH3), or a heater is used.

  Specifically, the dielectric constant of the insulating film is 2.50 or less, that is, a range including 2.40, 2.30, 2.20, 2.10, and 2.00, and any of these. .

In the present invention, the source gas used is disclosed in US patent application Ser. No. 10 / 317,239 filed on Dec. 11, 2002, which is incorporated herein by reference. The silicon-containing hydrocarbon compound represented by the general formula Si _α O _β C _x H _y (where α, β, x, and y are integers) is not limited to this, but includes at least one Si—O bond, Or a compound having at least two OC _n H _{2n + 1} bonds and at least two hydrocarbon radicals bonded to silicon. More specifically, the silicon-containing hydrocarbon compound includes at least one compound represented by the following chemical formula 2.

ここで、R1及びR2はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、m及びnは任意の整数である。

Here, R1 and R2 are any of CH3, C2H3, C2H5, C3H7, and C6H5, and m and n are arbitrary integers.

  In addition to the species described above, the silicon-containing hydrocarbon compound may include at least one compound represented by the following chemical formula 3.

ここで、R1、R2及びR3はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、nは任意の整数である。

Here, R1, R2 and R3 are any of CH3, C2H3, C2H5, C3H7 and C6H5, and n is an arbitrary integer.

  In addition to these species described above, the silicon-containing hydrocarbon compound may include at least one compound represented by the following chemical formula 4.

ここで、R1、R2、R3及びR4はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、ｍ及びnは任意の整数である。

Here, R1, R2, R3 and R4 are any of CH3, C2H3, C2H5, C3H7 and C6H5, and m and n are arbitrary integers.

  In addition to these species described above, the silicon-containing hydrocarbon compound can include at least one compound represented by the following chemical formula 5.

ここで、R1、R2、R3、R4、R5及びR6はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、添加ガスはアルゴン(Ar)、ヘリウム(He)及び酸化窒素(N2O)または酸素(O2)のいずれかである。

Here, R1, R2, R3, R4, R5 and R6 are either CH3, C2H3, C2H5, C3H7 and C6H5, and the additive gas is argon (Ar), helium (He) and nitrogen oxide (N2O) or oxygen (O2)

  Furthermore, other than these species described above, the silicon-containing hydrocarbon compound may include at least one compound represented by the following chemical formula 6.

ここで、R1、R2、R3及びR4はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、添加ガスはアルゴン(Ar)、ヘリウム(He)及び酸化窒素(N2O)または酸素(O2)のいずれかである。

Here, R1, R2, R3 and R4 are any of CH3, C2H3, C2H5, C3H7 and C6H5, and the additive gas is argon (Ar), helium (He) and nitrogen oxide (N2O) or oxygen (O2). Either.

  Furthermore, the source gas can contain at least one of the silicon-containing hydrocarbon compounds described above.

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

  The insulating film is formed on the substrate, and the film is polymerized by plasma energy in the plasma CVD apparatus using a source gas containing a silicon-containing hydrocarbon compound expressed by Chemical Formula 3.

  The insulating film is formed on the substrate, and the film is polymerized by plasma energy in the plasma CVD apparatus using a source gas containing a silicon-containing hydrocarbon compound expressed by Chemical Formula 4.

  Further, an insulating film is formed on the substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a source gas containing a silicon-containing hydrocarbon compound expressed by Chemical Formula 5.

  Furthermore, an insulating film is formed on the substrate, and the film is polymerized by plasma energy in a plasma CVD apparatus using a source gas containing a silicon-containing hydrocarbon compound expressed by Chemical Formula 6.

  According to another aspect of the present invention, the material for forming the insulating film is supplied in the vicinity of the substrate in a gas phase state, and is processed in a plasma CVD apparatus so as to form the insulating film on the substrate by a chemical reaction. The material is represented by Chemical Formula 2.

  In addition, the material for forming the insulating film is supplied in the vicinity of the substrate in a gas phase state, and is processed in the plasma CVD apparatus so as to form the insulating film on the substrate by a chemical reaction. The material is represented by Chemical Formula 3.

  The material for forming the insulating film is supplied in the vicinity of the substrate in a gas phase state, and is processed in the plasma CVD apparatus so as to form the insulating film on the substrate by a chemical reaction. The material is represented by Chemical Formula 4.

  Furthermore, the material for forming the insulating film is supplied to the vicinity of the substrate in a gas phase together with either nitric oxide (N2O) or oxygen (O2) as an oxidant, and plasma is formed so that the insulating film is formed on the substrate by a chemical reaction. Processed in CVD equipment. The material is a compound represented by Chemical Formula 5.

  Furthermore, the material for forming the insulating film is supplied to the vicinity of the substrate in a gas phase together with either nitric oxide (N2O) or oxygen (O2) as an oxidizing agent, and forms an insulating film on the substrate by a chemical reaction. Processed in plasma CVD equipment. The material is a compound represented by Chemical Formula 6.

The reaction gas residence time Rt (according to the above definition) is determined based on the reaction chamber volume, reaction pressure, and total reaction gas flow rate for the reaction. In order to maintain a stable plasma, the reaction pressure is usually 1 to 10 Torr, preferably 3 to 7 Torr. This reaction pressure is relatively high in order to extend the residence time of the reaction gas. The total flow rate of the reaction gas is important for reducing the relative dielectric constant of the produced film. There is no need to control the ratio of source gas to additive gas. In general, the longer the residence time, the lower the dielectric constant. The flow rate of the source gas required for film formation depends on the desired deposition rate and the area of the substrate on which the film is formed. For example, in order to form a film on a substrate with a radius r = 100 mm at a deposition rate of 300 nm / min, a source gas of at least 50 sccm should be included in the reaction gas. This is approximately 1.6 × 10 ² sccm per substrate surface area (m ² ). 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 ≦ Rt, more preferably 200 msec ≦ Rt ≦ 5 sec. In conventional plasma TEOS, Rt is generally in the range of 10-30 msec.

  In the above, the average reaction temperature (Tr) is the average reaction gas temperature at the substrate, which is determined by measuring the temperature of the susceptor. The reaction gas consists of a source gas (ie, a material gas or a precursor gas) and an additive gas (eg, a carrier gas, an oxidizing gas, a plasma stabilizing gas, etc.). If no additive gas is used, the source gas itself corresponds to the reaction gas.

In the above, the residence time means the average time interval during which gas molecules stay in the reaction chamber. Residence time Rt is calculated by Rt = αV / S. Where V is the chamber capacity (cc), S is the reaction gas volume (cc / s), and α is determined by the shape of the reaction chamber and the positional relationship between the gas inlet and outlet. Is a coefficient. The reaction space in the reaction chamber is defined by the surface of the substrate (πr ² ) and the distance between the upper electrode and the lower electrode. Considering the flow rate of gas flowing through the reaction space, α is estimated to be ½. In the above equation, α is ½.

In this method, in short, the source gas is a silicon-containing hydrocarbon compound comprising at least one Si-O bond, at most two OC _n H _{2n + 1} bonds, and at least two hydrocarbon radicals bonded to silicon. It is. Moreover, this source gas is vaporized by the direct vaporization method. The method produces an insulating film having a low dielectric constant, high thermal stability, and high moisture resistance.

  More specifically, the source gas vaporized by the direct vaporization method can remain in the plasma for a sufficiently long time. As a result, a linear polymer is formed, and as a result, a linear polymer having a basic structure (Chemical Formula 7) in which n is an integer value of 2 or more is formed in the gas phase. Thereafter, the polymer is deposited on the semiconductor substrate to form a film having a microporous structure.

ここで、X1及びX2はOnCmHpであり、nは０または１、m及びpはゼロを含む整数である。

Here, X1 and X2 are OnCmHp, n is 0 or 1, and m and p are integers including zero.

  The insulating film of the present invention has relatively high stability because the basic structure has Si—O bonds with high binding energy. Moreover, since it has a microporous structure, its dielectric constant is low. Furthermore, the basic structure (-SiO-) n on both sides has dangling bonds terminated with hydrophobically treated hydrocarbon radicals, and this property provides moisture resistance. Furthermore, the bonds between hydrocarbon radicals and silicon are generally stable. For example, both the Si—CH3 bond with the methyl radical and the Si—C6H5 bond with benzene have a dissociation temperature of 500 ° C. or higher. Since the semiconductor manufacturing requires thermal stability at a temperature of 450 ° C. or higher, the characteristics of the film are advantageous for semiconductor manufacturing.

  Other aspects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments.

  FIG. 1 illustrates a plasma CVD apparatus that can be used in the present invention. The apparatus includes a reactive gas supply device 12 and a plasma CVD device 1. The reactive gas supply device 12 includes a plurality of lines 13, a control valve 8 and gas inlets 14, 15 and 16 arranged in the lines 13. A flow controller 7 is connected to each control valve 8 to control the flow of a predetermined volume of source gas. A container containing the liquid reaction material 18 is connected to a vaporizer 17 that directly vaporizes the liquid. The plasma CVD apparatus 1 includes a reaction chamber 6, a gas inlet 5, a susceptor 3 and a heater 2. A circular gas diffusion plate 10 is arranged immediately below the gas inlet. The gas diffusion plate 10 has a large number of pores on the bottom surface, from which reaction gas can be injected onto the semiconductor substrate 4. There is an exhaust port 11 at the bottom of the reaction chamber 6. The exhaust port 11 is connected to an external vacuum pump (not shown), and the inside of the reaction chamber 6 is evacuated. The susceptor 3 is arranged in parallel and facing the gas diffusion plate 10. The susceptor 3 holds the semiconductor substrate 4 thereon and is heated by the heater 2. The gas inlet 5 is insulated from the reaction chamber 6 and connected to an external high-frequency power source 9. Alternatively, the susceptor 3 may be connected to the power source 9. The gas diffusion plate 10 and the susceptor 3 act as high-frequency electrodes, and generate a plasma reaction field near the surface of the semiconductor substrate 4.

A method of forming an insulating film on a semiconductor substrate using the plasma CVD apparatus of the present invention is a silicon-containing hydrocarbon represented by the general formula Si _α O _β C _x H _y (α, β, x and y are integers). The step of directly vaporizing the compound and then introducing it into the reaction chamber 6 of the plasma CVD apparatus 1, the step of introducing an additive gas having a substantially reduced flow rate into the reaction chamber 6, and the plasma polymerization reaction on the semiconductor substrate A step of forming an insulating film, in which a mixed gas made from a silicon-containing hydrocarbon compound as a source gas and an additive gas is used as a reaction gas. It is a noteworthy feature that the reduction in additive gas flow results in a substantial reduction in the total flow of the reaction gas. This feature is described in more detail below.

In this regard, the silicon-containing hydrocarbon compound represented by the general formula Si _α O _β C _x H _y (where α, β, x and y are integers) is preferably at least one Si—O bond, two Alternatively, it is a compound having an OC _n H _{2n + 1} bond of less than that and at least two hydrocarbon radicals bonded to silicon. More specifically, it is the compound shown below.
Compound (A)

ここで、R1及びR2はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、ｍ及びｎは任意の整数である。
化合物(B)

Here, R1 and R2 are any of CH3, C2H3, C2H5, C3H7, and C6H5, and m and n are arbitrary integers.
Compound (B)

ここで、R1、R2及びR3はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、ｎは任意の整数である。
化合物(C)

Here, R1, R2 and R3 are any one of CH3, C2H3, C2H5, C3H7 and C6H5, and n is an arbitrary integer.
Compound (C)

ここで、R1、R2、R3及びR4はCH3、C2H3、C2H5、C3H7及びC6H5のいずれかであり、ｍ及びｎは任意の整数である。
化合物(D)

Here, R1, R2, R3 and R4 are any one of CH3, C2H3, C2H5, C3H7 and C6H5, and m and n are arbitrary integers.
Compound (D)

ここで、R1、R2、R3、R4、R5及びR6はCH3、C2H3、C2H5、C3H7及びC6H5、並びに酸化剤としての酸化窒素(N2O)または酸素(O2)を有する化合物の混合物のいずれかである。
化合物(E)

Where R1, R2, R3, R4, R5 and R6 are either CH3, C2H3, C2H5, C3H7 and C6H5 and a mixture of compounds having nitric oxide (N2O) or oxygen (O2) as oxidants. .
Compound (E)

ここで、R1、R2、R3及びR4はCH3、C2H3、C2H5、C3H7及びC6H5、並びに酸化剤としての酸化窒素(N2O)または酸素(O2)を有する化合物の混合物のいずれかである。

Here, R1, R2, R3 and R4 are any of CH3, C2H3, C2H5, C3H7 and C6H5, and a mixture of compounds having nitrogen oxide (N2O) or oxygen (O2) as oxidants.

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

  More specifically, the additive gases used in this example are argon gas and helium gas. In essence, argon is used for plasma stabilization and helium is used to improve plasma uniformity and insulation film thickness uniformity.

  In the above method, the direct vaporization in the first step is a method in which a liquid material whose flow rate is controlled is instantaneously vaporized by a preheated vaporizer. This direct vaporization method does not require a carrier gas such as argon to obtain a specified amount of source gas. This is very different from the bubbling method. Therefore, a large amount of argon gas or helium gas is no longer needed, which reduces the total gas flow rate of the reaction gas and consequently increases the time that the source gas stays in the plasma. As a result, a sufficient polymerization reaction occurs in the gas phase, resulting in the formation of a linear polymer and a membrane having a microporous structure.

  In FIG. 1, the inert gas supplied through the gas inlet 14 pushes the liquid reaction material 18, which is a silicon-containing hydrocarbon compound, to the control valve 8 through the line 13. 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. The reduced silicon-containing hydrocarbon compound goes to the vaporizer 17 and is vaporized by the direct vaporization method described above. Argon and helium are supplied through inlets 15 and 16, respectively, and valve 8 controls the flow rates of these gases. The mixture of source gas and additive gas, which is a reactive gas, is then supplied to the inlet 5 of the plasma CVD apparatus 1. The space between the gas diffusion plate 10 and the semiconductor substrate 4 disposed inside the reaction chamber 6 that has already been evacuated is preferably 13.4 MHz superimposed with low-frequency RF power having a frequency of 430 kHz. High frequency RF power having a frequency is applied, and the space acts as a plasma field. The susceptor 3 continuously heats the semiconductor substrate 4 by the heater 2 and 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 is not sufficiently deposited, and as a result, the film deposited on the substrate does not form a microporous structure. Since the residence time is inversely proportional to the flow rate of the reaction gas, a decrease in the reaction gas flow rate can extend the residence time.

  In order to significantly reduce the total volume of the reaction gas, it is effective to reduce the flow rate of the additive gas. As a result, the residence time of the reaction gas is extended, and as a result, the linear polymer is sufficiently deposited, and subsequently an insulating film having a microporous structure is formed.

  In order to regulate the reaction in the gas phase, it is effective to add a small amount of inert gas, oxidizing agent or reducing agent to the reaction chamber. Helium (He) and argon (Ar) are inert gases and have different first ionization energies of 24.56 eV and 15.76 eV, respectively. Therefore, the reaction of the source gas in the gas phase is controlled by adding He or Ar alone or a combination of both in a predetermined amount. The molecules of the reaction gas undergo polymerization in the gas phase, thereby forming oligomers. The oligomer is expected to have a 1: 1 O: Si ratio. However, when the oligomer forms a film on the substrate, the oligomer undergoes further polymerization, producing a higher oxygen ratio. The ratio depends on the dielectric constant or other properties of the film formed on the substrate (eg, in Example 5 described below, the ratio is 3: 2).

  Residual oxygen that is extracted from the source gas and not incorporated into the film is dissociated from the material compound and floats in the plasma. The ratio of Si: O in the source gas varies depending on the compound. For example, in the chemical formulas (A) to (E), the ratio of O: Si is 2: 1, 1: 1, 3: 2, 1: 2, and 0: 1, respectively. If a source gas having a high ratio of O: Si (eg 3/2 or more) is used, the amount of oxygen floating in the plasma will increase. When the amount of oxygen increases, organic groups that are directly bonded to silicon and necessary for film formation are oxidized, and as a result, film deterioration is likely to occur. In the above, by adding reducing agents such as H2 and CH4 to the reaction chamber, the oxygen partial pressure in the plasma is reduced, thereby preventing the oxidation of the organic groups. In contrast, when the O: Si ratio is low (eg, 3/2 or less), it is necessary to supply the deposition oxygen by adding oxidizing agents such as N 2 O and O 2. The appropriate amount of reducing or oxidizing agent is pre-evaluated based on preliminary experiments where the composition and relative permittivity of the film formed are analyzed by FT-IR or XRS. Thus, by selecting the appropriate type of additive gas, such as He, Ar, reducing agent and oxidant, and controlling the amount of each gas to be added, a film with the desired quality is produced.

In the above, the silicon-containing hydrocarbon compound that generates the source gas for the silicon polymer preferably has two or less alkoxy groups or no alkoxy groups. The use of a source gas having three or more alkoxy groups prevents the formation of a linear silicon polymer, resulting in a relatively high dielectric constant film. In the above, the number of Si atoms is limited (the larger the number of Si atoms, the more difficult it is to vaporize and the higher the cost of synthesizing the compound), but one molecule of the compound is preferably one, Contains 2 or 3 Si atoms. Alkoxy groups usually contain 1 to 3 carbon atoms, preferably 1 or 2 carbon atoms. The hydrocarbon bonded to Si usually has 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. Suitable silicon-containing hydrocarbon compounds have the following chemical formula:
Si _α O _α-1 R _{2α-β + 2} (OC _n H _{2n + 1} ) _β
Here, α is an integer of 1 to 3, β is 0, 1 or 2, n is an integer of 1 to 3, and R is a C _1-6 hydrocarbon bonded to Si. The use of an oxidant or a reducing agent can be used to achieve a target relative dielectric constant (3.30 or lower, preferably 3.10 or lower, more preferably 2.80 or lower) and relative dielectric constant of the silicon polymer film. It depends on other properties such as rate stability and thermal stability. The O: Si ratio in the source gas is also taken into account for selecting the oxidizing agent or reducing agent as described above. Preferably, an oxidizing agent is used if the ratio is lower than 3: 2, and a reducing agent is used if it is higher than 3: 2. In addition, inert gases such as Ar and He are for controlling the plasma reaction, but are not essential for forming a silicon polymer film. The flow rate of the source gas and the flow rate of the additive gas vary depending on the plasma CVD apparatus. The appropriate flow rate is determined by correlating the relative dielectric constant of the silicon polymer film with the residence time of the reaction gas (consisting of source gas and additive gas). The longer the residence time, the lower the dielectric constant. The reduction rate of the dielectric constant per extended residence time is variable, and after a certain residence time, the reduction rate of the dielectric constant increases. That is, the dielectric constant drops sharply after a certain residence time of the reaction gas. After this relative permittivity fall range, the relative permittivity decrease is slow. This is very interesting. In the present invention, the relative dielectric constant of the silicon polymer film is extended by extending the residence time until reaching the range of decrease in relative dielectric constant based on a predetermined correlation between the dielectric constant of the film and the residence time of the reaction gas. The rate can be greatly reduced.

Examples Experiments were performed using DM-DMOS (dimethyldimethoxysilane) as described below. Conditions and results are shown in the following table (see the residence time equation for a description of the symbols). In these experiments, a normal plasma CVD apparatus (EAGLE-10 (trademark) manufactured by Japan ASM Co., Ltd.) was used as the experimental apparatus. here,
r _w (radius of silicon substrate): 0.1 m
d (distance between the silicon substrate and the upper electrode): 0.024 m
P _s (standard atmospheric pressure): 1.01 × 10 ⁵ Pa
T _s (standard temperature): 273K
The dielectric constant was measured after heating the film at 420 ° C. in vacuum to remove excess moisture. The reaction temperature (T _r ) is the temperature of the susceptor, which is substantially equal to the temperature on the substrate corresponding to the reaction temperature.

  Table 1 lists comparative examples and examples of the present invention.

表中に示されているように、比較例１及び２において、反応温度は低いが、滞留時間は短く（流量は多い）、比較的高い比誘電率を生じさせた。対照的に、実施例１において、反応温度が低くかつ滞留時間が長いため、膜の比誘電率は非常に低かった（２.２５）。比較例１において、たとえ滞留時間が長くても、反応温度が高かったため、生成膜は実施例１の膜ほど低い比誘電率を有しなかった。

As shown in the table, in Comparative Examples 1 and 2, the reaction temperature was low, but the residence time was short (the flow rate was large), and a relatively high dielectric constant was generated. In contrast, in Example 1, the dielectric constant of the film was very low (2.25) due to the low reaction temperature and long residence time. In Comparative Example 1, even if the residence time was long, the reaction temperature was high, so that the resulting film did not have a lower relative dielectric constant than the film of Example 1.

FIG. 2 is an FT-IR profile (infrared absorption spectrum) showing the structures of the films of Comparative Example 4 and Example 1. The absorption peak at 1275 cm ⁻¹ represents the Si—CH 3 bond, and the absorption peak at 800 cm ⁻¹ represents the Si (CH 3) 2 bond. In Example 1, the absorption peak is much larger than that of Comparative Example 4, which indicates that the film of Example 1 has a (—Si (CH 3) 2 —O—) n structure close to the ideal siloxane polymer. Show.

  While the invention has been described in terms of certain embodiments, it will be apparent to those skilled in the art that other embodiments exist within the scope of the invention. Accordingly, aspects of the invention should be defined only by the claims. The present invention includes various embodiments and is not limited to the above embodiments. In particular, the present invention includes, but is not limited to, the following examples, and any combination of the above examples and the following examples can be easily achieved.

  In the present invention, the reaction space is not limited to a physically defined single compartment, but includes any suitable space for plasma reactions. That is, as those skilled in the art can easily understand, the space is a functionally defined reaction space. The space may consist of a physically defined single compartment, such as the interior of the reactor, or a plurality of physically defined compartments that communicate with each other with respect to the plasma reaction, such as the interior of the remote plasma chamber and the interior of the reactor. it can. Further, the space includes the inside of a pipe that connects a plurality of compartments through which the reaction gas passes. The interior of the reactor contains only the space used for the plasma reaction. Therefore, when the reactor is composed of a plurality of compartments, if only a part inside the reactor is used for the plasma reaction, only the part used for the plasma reaction constitutes the reaction space. The plasma reaction includes a preliminary reaction for plasma polymerization.

  Those skilled in the art will recognize that various modifications can be made without departing from the spirit of the present invention. Accordingly, the form of the invention is illustrative only and is not intended to limit the aspects of the invention.

FIG. 1 is a schematic view showing a plasma CVD apparatus used for forming an insulating film of the present invention. FIG. 2 is an FT-IR profile (infrared absorption spectrum) showing the structure of the formed film obtained in Examples and Comparative Examples of the present invention.

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 RF power supply
10 Gas diffusion plate
11 Gas exhaust port
12 Reaction gas supply device
13 lines
14 Gas inlet
15 Gas inlet
16 Gas inlet
17 Vaporizer
18 Liquid reaction materials

Claims (19)

A method of forming an insulating film on a semiconductor substrate by plasma reaction,
Vaporizing the silicon-containing hydrocarbon compound to provide a source gas;
Introducing a source gas into the reaction space for plasma CVD processing where the semiconductor substrate is disposed;
Optionally introducing an additive gas selected from the group consisting of a carrier gas, an oxidizing gas and a plasma stabilizing gas, wherein the source gas and the additive gas constitute a reactive gas; and
A process of forming an insulating film on a semiconductor substrate by activating a plasma polymerization reaction at a temperature of about −50 ° C. to about 100 ° C. in the reaction space, wherein the plasma polymerization reaction is a reaction gas in the reaction space. It is activated while controlling the flow rate of the reaction gas so as to extend the residence time Rt, and 100 msec ≦ Rt,
Rt [s] ＝ 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F
here,
Pr: Reaction space pressure (Pa)
Ps: Standard atmospheric pressure (Pa)
Tr: Average reaction temperature (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 reactive gas (sccm)
And where the process is
A method consisting of: The method of claim 1, wherein the reaction temperature is from about -10 ° C to about 50 ° C. 2. The method according to claim 1, wherein a carrier gas is introduced into the reaction space, and the carrier gas is an inert gas selected from the group consisting of Ar, Ne and He. 2. The method according to claim 1, wherein an oxidizing gas is introduced into the reaction space, and the oxidizing gas is selected from the group consisting of O2, NO, CO2 and N2O. The method of claim 1, wherein a plasma stabilizing gas is introduced into the reaction space, the plasma stabilizing gas having the chemical formula CxHyOz (where x, y and z are integers), at least one of Selected from the group consisting of C _1-4 alkanols, C _2-4 ethers, C _4-12 aromatic hydrocarbons, C _4-12 alicyclic hydrocarbons, and cyclic aldehydes (CH 2 O) n (3 ≦ n ≦ 6) Where is the way. 2. The method of claim 1, wherein the residence time Rt is about 200 msec or more. The method according to claim 1, further comprising annealing the insulating film. 8. The method according to claim 7, wherein the annealing is performed under a reduced pressure by radiating the insulating film with a plasma using ultraviolet rays, infrared rays, electron beams or inert gas and / or a reducing gas such as H2 or NH3. Wherein the process is carried out at a temperature of from about 300 ° C to about 450 ° C. 2. The method according to claim 1, wherein the flow rate of the reaction gas is controlled so that the dielectric constant of the insulating film is 2.50 or less. The method according to claim 1, wherein the silicon-containing hydrocarbon has the formula _{Si α O α-1 R 2α} -β + 2 (OC n H 2n + 1) have the _beta, where, alpha is 1 to 3 An integer, β is an integer from 0 to 2, n is an integer from 1 to 3, and R is a C _1-6 hydrocarbon bonded to Si, whereby a siloxane weight having a repeating structural unit of —SiR ₂ O— A method in which the combined film is formed as an insulating film. 11. The method according to claim 10, wherein the silicon-containing hydrocarbon compound has two alkoxy groups ([beta] = 2). 11. The method according to claim 10, wherein the alkoxy present in the silicon-containing hydrocarbon has 1 to 3 carbon atoms. 11. The method according to claim 10, wherein the hydrocarbon present in the silicon-containing hydrocarbon compound has 1 to 6 carbon atoms (n = 1-6). 11. The method according to claim 10, wherein the silicon-containing hydrocarbon compound has 1 to 3 silicon atoms. 11. The method according to claim 10, wherein the silicon-containing hydrocarbon compound has 1 or 2 silicon atoms (α = 1 or 2). A method of forming an insulating film on a semiconductor substrate by plasma reaction,
Vaporizing the silicon-containing hydrocarbon compound to provide a source gas;
Introducing a source gas into the reaction space for plasma CVD processing where the semiconductor substrate is disposed;
Introducing an additive gas selected from the group consisting of a carrier gas, an oxidizing gas and a plasma stabilizing gas, wherein the source gas and the additive gas constitute a reactive gas; and
A process of forming an insulating film on a semiconductor substrate by activating a plasma polymerization reaction at a temperature of about −50 ° C. to about 100 ° C. in the reaction space, wherein the plasma polymerization reaction is a reaction gas in the reaction space. It is activated while controlling the flow rate of the reaction gas so as to extend the residence time Rt, and 100 msec ≦ Rt,
Rt [s] ＝ 9.42 × 10 ⁷ (Pr ・ Ts / Ps ・ Tr) r _w ² d / F
here,
Pr: Reaction space pressure (Pa)
Ps: Standard atmospheric pressure (Pa)
Tr: Average reaction temperature (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 reactive gas (sccm)
And where the process is
Annealing the insulating film at a temperature of about 300 ° C. to about 450 ° C. to remove moisture from the insulating film and increase its mechanical strength;
A method consisting of: The method of claim 16, wherein the reaction temperature is from about -10 ° C to about 50 ° C. The method according to claim 16, wherein the residence time Rt is about 200 msec or more. 17. The method according to claim 16, wherein the annealing is performed under a reduced pressure by radiating the insulating film with a plasma using ultraviolet rays, infrared rays, an electron beam or an inert gas and / or a reducing gas such as H2 or NH3. Wherein the process is carried out at a temperature of from about 300 ° C to about 450 ° C.

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