JPH10135206A - Formation of sio2 film by plasma cvd - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an SiO2 insulating film according to plasma CVD, capable of achieving higher speed film deposition, higher film adhesion, and higher film hardness. SOLUTION: A magnetic field is applied in a plasma generating chamber 1 by a magnetic coil 2 arranged around the plasma generating chamber 1, a microwave of 100-200W is introduced into the plasma-generating chamber 1, an upstream-gas is introduced into the plasma-generating chamber for generating ECR plasma, a raw material is vaporized downstream to generate the gas to be supplied. This gas is supplied from the inlet, and further the ECR(electron cyclotron resonance) plasma is passed through a mesh provided between the inlet 6 and a substrate 7 or between the plasma-generating chamber 1 and the inlet, and the substrate is made not to be heated, thus an SiO2 film is deposited on the surface of the substrate. The substrate is heated to 150-300 deg.C, preferably to a temperature not lower than 150 deg.C and higher than 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a SiO ₂ thin film by plasma CVD.

[0002]

2. Description of the Related Art In recent years, LSIs (La
rge Scale Integrated Cir
With advancement of miniaturization and high integration of the unit, an advanced technique is required for a method of depositing an interlayer insulating film of a multilayer wiring or an SiO ₂ film used for protective coating. Among many deposition methods, ECR plasma CVD (Ele
ctron Cycloton Resonance
Plasma Chemical Vapor Dep
position) is expected as a method that can efficiently deposit a high-quality SiO ₂ insulating film at a low temperature at a high ionization rate of a reaction gas.

[0003] SiO used for LSI_TwoFor insulating film deposition
Is a step cover with better gap fill characteristics.
Ledge properties, reduced film deposition temperature (<400 ° C), film
H in _TwoReduction of O, -OH, C, high film deposition rate
Function such as high film adhesion, high film hardness, etc.
Is required. Currently, in response to such demands,
Zuma CVD, thermal CVD, low pressure CVD, ozone, etc.
An approach has been attempted. However, it must meet all requirements.
Deposition of the rim is extremely difficult. In particular, film deposition rate, film
Adhesion and film hardness are not satisfactory
won.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to form a SiO ₂ insulating film by plasma CVD, particularly to increase the film deposition rate, obtain high film adhesion and high film hardness. It is to provide a method.

[0005]

Means for Solving the Problems To achieve the above object,
Therefore, the invention described in claim 1 is based on plasma CVD.
SiO_TwoIn the method of forming a thin film, the periphery of the plasma generation chamber is
The magnetic coil placed in the
Applying a magnetic field and pulsing a microwave of 100 to 200 W
Into the gas generation chamber to generate plasma from upstream gas
Introduces ECR plasma into living room,
The feed gas is generated by vaporizing the raw material in the
The supply gas is supplied from the inlet, and further, the inlet and the substrate
Or between the plasma generation chamber and the inlet
Pass the ECR plasma through the mesh
Do not heat the substrate, so that the substrate surface
SiO_TwoCharacterized in that a film is deposited
You. The invention described in claim 2 is based on plasma CVD.
SiO_TwoIn the method of forming a thin film, the periphery of the plasma generation chamber is
The magnetic coil placed in the
Apply a magnetic field, introduce microwaves into the plasma generation chamber,
Upstream gas is introduced into the plasma generation chamber and
Generates CR plasma and concentrates raw materials downstream
To produce a supply gas, and supply the gas from the inlet
And further between the inlet and the substrate or the
To the mesh installed between the chamber and the inlet
Pass the ECR plasma and set the substrate temperature to 150 to 300
° C, thereby forming SiO 2 on the substrate surface._TwoDeposit the film
It is characterized by doing so. Claim 3
According to the invention, plasma CVD is used.
SiO _TwoIn the method of forming a thin film, the substrate temperature is set to 150 ° C. or less.
Characterized in that it is heated to below 200 ° C.
You.

[0006]

FIG. 1 shows an embodiment of an apparatus used for a method of forming an SiO ₂ insulating film by plasma CVD according to the present invention. This device is a horizontal ECR
In the plasma CVD apparatus, a magnetic coil 2 is arranged around the plasma generation chamber 1, a magnetic field that is an ECR condition is applied to the inside of the plasma generation chamber 1, and microwaves are introduced 3 into the generation chamber 1 to generate plasma. 3a is a quartz glass. The magnetic field distribution of the magnetic coil 2 is of a divergent magnetic field type that decreases from the plasma generation chamber 1 to the sample chamber 4. The upstream gas is flow-controlled by the mass flow controller and introduced into the plasma generation chamber 5 to generate ECR plasma.

[0007] The raw material liquid is heated and vaporized in the downstream thereof, and the gas is flow-controlled to control the ring-shaped inlet 6.
And a SiO ₂ film can be deposited on the surface of the substrate 7. The source gas supply system includes a source gas tank, a source gas supply line, a purge gas supply line,
Including FC devices. In this apparatus, a source gas from a gas supply line is temporarily stored in a source gas tank, and the source gas is mixed with a purge gas (eg, N ₂ ) from a purge gas supply line by an MFC device, and a predetermined amount is passed through a supply line 13. From the inlet 6. The inlet 6 has a plurality of small holes formed in the inner peripheral surface of the ring tube so that the gas can uniformly flow out of the small holes. Further, in the apparatus shown in FIG. 1, cooling water is supplied from the cooling water supply port 17,
The cooling water is discharged from the cooling water discharge port 18. 7a is a heating device for the substrate 7.

Further, in this apparatus, the circular mesh 14 connected to the ground is connected to the ring-shaped supply gas inlet 6 and the substrate 7.
It is installed between The mesh 14 is generally made of metal, and is grounded or a DC positive or negative voltage is applied. The mesh 14 has a role of catching electrons in the plasma, escaping to the ground, and passing only radicals (neutrons) in the plasma, so that the diameter of the mesh and the size of the wire grid are important. The mesh 14 must be larger than the diameter of the ring-shaped feed gas inlet 6 and the diameter of the plasma stream 16 at this point to be generated. For example, when the mesh 14 is made of a stainless steel wire, if the mesh is too thick, the shadow of the wire is transferred to the surface of the formed film and becomes uneven, so that the mesh 14 must be thin to some extent. Therefore, the diameter of the wire is preferably φ0.1 mm or more and 1 mm or less. If the lattice size of the mesh 14 is too large, electrons in the plasma cannot be trapped and pass through the mesh 14 together with radicals.
Therefore, it is preferably 5 mm × 5 mm or less. However,
The shape of the grating is not limited, and may be, for example, an octagon, and the area size of one grating is preferably 25 mm ² or less.

The position of the mesh 14 installed in the ECR plasma CVD apparatus and the ring-shaped supply gas inlet 6
Matching of the positional relationship between the substrate 7 (plastic, metal, ceramics, and material is not particularly limited) is important for forming a SiO ₂ film at low temperature and high speed. It is desirable that the position where the mesh 14 is installed is not close to the substrate side of the ring-shaped supply gas inlet 6, but the closer to the ring-shaped supply gas inlet 6, the higher the deposition rate of the SiO ₂ film is. It is also effective to install a mesh 14 in the plasma generation chamber 1 or between the plasma generation chamber 1 and the ring-shaped supply gas inlet 6.

The amount of electrons, negative ions and positive ions in the plasma can be controlled by grounding the mesh 14 or applying a DC voltage from negative to positive. DC voltage from -50V to +
When the voltage is applied in the range of 50, the film forming speed increases. In particular, when the OV, that is, the mesh 14 is only grounded and no voltage is applied, the effect of trapping electrons in the plasma is the highest, and the film forming speed is significantly increased. In order to increase the deposition rate of the SiO ₂ film, it is preferable to ground the mesh 14. When applying a DC voltage to the mesh 14,
The mesh 14 must be completely insulated from the reaction chamber.

The substrate 7 to which the present invention is applied can be widely used for semiconductor devices. In addition, as a raw material of the supply gas to be deposited, tetraethoxysilane (hereinafter referred to as TEOS) is a Si-containing compound represented by the following formula I.

[0012]

Embedded image The gas supplied to the upstream includes O ₂ , C
O, H ₂ , He, Ar and the like can be mentioned.

In order to coat high-quality SiO ₂ containing no impurities without excessively heating the substrate, it is necessary to precisely control the generated plasma conditions. Conventionally, when an ECR plasma is generated in a plasma generation chamber and an SiO ₂ insulating film is deposited on the substrate by the ECR plasma, the temperature of the substrate is set to 200 to 400 without using the metal mesh.
The temperature was controlled in the range of ° C. If the temperature is lower than 200 ° C., the use of a metal mesh is not preferable because the migration (fluidity) of the precursor adsorbed on the substrate surface is reduced. On the other hand, if the temperature exceeds 400 ° C., thermal damage is given to the Al wiring substrate (stress, crack, etc.), which is not preferable. Therefore, when a metal mesh is not used, the range of 200 to 400 ° C. has been considered to be optimal.

In the present invention, conditions for obtaining satisfactory characteristics have been created when a metal mesh is used. First, as understood from the examples described later, the output of the microwave introduced into the plasma generation chamber is 100 to 2
It is preferably 00W. Thereby, SiO ₂
High-speed film deposition and high adhesion can be obtained. Similarly, as will be understood from the examples described later, when a mesh is used, the substrate temperature is preferably heated to 150 to 300 ° C. This makes it possible to increase the speed of depositing the SiO ₂ film and obtain high hardness. However, even if the substrate is heated to 200 ° C. or higher using a mesh, the adhesion of SiO ₂ is not improved. Therefore, it is preferable to heat the substrate to 150 ° C. or higher and lower than 200 ° C. The supply rate of the supply gas such as TEOS is 1.5 sccm (abbreviation of standard cc / min, cc / min (at 25 ° C.) in SI unit system) or less, preferably in the range of 0.5 to 1.5 sccm. Is good. 1.5sc
cm, the content of carbon, which is an impurity in the film, is significantly increased, and the film quality is deteriorated. 0.5scc
If it is less than m, the film formation rate will be significantly reduced.

[0015]

EXAMPLES Using an ECR plasma CVD apparatus of Embodiment FIG 1, was performed a thin film forming experiments. The experimental conditions and results are shown below. The deposition process embodiment of the SiO ₂ film was placed a magnetic coil around the plasma generation chamber 1, and applying a magnetic field of flux density 875Gauss is ECR condition to the plasma generating chamber. High-purity oxygen gas was introduced as an upstream gas into the plasma generation chamber 1 to generate ECR plasma. High-purity TEOS gas was introduced into the downstream from the ring-shaped gas inlet 6, and a film was deposited on a single crystal silicon (Si <100>) and a silicon substrate 7 having a half-micron size Al wiring step pattern. Since TEOS is liquid at room temperature and direct gas introduction is impossible, TEOS is heated to 80 ° C by a heating system, TEOS is directly gasified, and the flow rate is controlled by a mass flow controller.
It was introduced into the reaction chamber. The piping to the reaction chamber and the mass flow controller were also heated to prevent dew condensation in the tubes.
Further, in order to investigate the plasma characteristics at the time of depositing the SiO ₂ film, the emission spectrum of the plasma was measured using a spectroscope. Table 1 shows the ECR plasma CVD conditions for depositing the SiO ₂ film obtained from the preliminary experiment.

[0016]

[Table 1]

Measurement of micro hardness and adhesion strength The micro hardness of the SiO ₂ film deposited on the silicon wafer is as follows.
Micro dynamic hardness tester (Shimadzu Corporation, DUH
-50). In this method, a diamond chip (a pyramid having an edge angle of 115 °) is pressed into the substrate surface at a constant load speed (0.048 gf / sec). The micro dynamic hardness is calculated from the following equation. Microdynamic hardness = α × P / D ² where α is a coefficient (=
37.838), P is the indentation load (gf), and D is the indentation depth (μm). In this example, the depth of the diamond chip was set to 0.8 μm from the film surface. FIG. 2 shows the relationship between dynamic hardness and Vickers hardness for reference. This result was calculated from a preliminary experiment. Furthermore, S
The adhesion strength of the SiO ₂ film deposited on the i-substrate was measured by a scratch-type adhesion strength meter (SST-10, Shimadzu Corporation).
0)). In this method, the deposited film on the substrate surface is kept at a constant speed (20 μm / sec) by a diamond needle.
c) Scratched. The amplitude of the scratch was 10 μm, and the maximum load of the scratch needle was 10 gf. The critical load when the film was peeled off by the scratch test was read directly. To determine the adhesion strength, use Benjamin and Wea
The following equation of ver was used. Adhesion strength = H / {(πR ² H / Wc) −1} ^1/2 where H is the substrate (Si (100) = 767 kgf / m)
Brinell hardness m ^2), R is the diamond stylus radius ^{(1.5 × 10 -3 mm),} Wc is the critical load of film adhesion (k
gf).

Microwave power affects film hardness and adhesion
The affect microwave power and the deposition rate of the relationship at room temperature shown in FIG. When a mesh is used, a high deposition rate is observed. This is presumably because the mesh reduced electrons and ions in the downstream plasma and reduced the etching reaction between the deposited film and the precursor adsorbed on the substrate.
On the other hand, when the microwave output increases from 100 W to 150 W, the deposition rate increases. However, microwaves are 200
When increasing to W, the deposition rate is lower than the deposition rate obtained at 100W. This is thought to be due to the competition between the increase in radicals and ions and the increase in deposition and etching reactions. Further, all the deposited films had a carbon content of 2.5% or less and a refractive index of 1.45. This is considered that a film having the same characteristics was deposited. FIG. 4 shows the relationship between the microwave output and the hardness of the substrate surface on which the SiO ₂ film was deposited with or without the mesh. The deposition was performed at room temperature. All film hardness was a constant value of 39 (DH115 °). This is probably because the deposited films have the same characteristics. Furthermore, the microwave output and the Si deposited on the Si substrate
FIG. 5 shows the relationship between the adhesion of the O ₂ film. In both cases with and without the mesh, the film adhesion increased as the microwave output increased. This is considered to be because only the film with high adhesion was deposited on the substrate surface because the film or precursor adsorbed with low adhesion was etched by high microwave power.

Effect of Substrate Temperature on Hardness and Adhesion FIG. 6 shows an Arrhenius plot of the deposition rate with respect to the substrate temperature. A relatively high deposition rate is observed when using a mesh. 2 for both with and without mesh
Negative activation energy is obtained in a temperature range of 00 ° C. or higher. The negative activation energy suggests that the adsorption / desorption reaction on the substrate surface is also proceeding in addition to the reaction process. Therefore, the following reaction stages of SiO ₂ deposition are conceivable. It is decomposed by oxygen radicals flowing from the upstream plasma, and a precursor of SiO ₂ is generated in the gas phase. TEOS + O ^* → precursor + byproduct (gas phase reaction) The molecules of the precursor adsorbed on the substrate surface undergo a bombardment reaction due to oxygen radicals for forming a SiO ₂ film. Precursor + O ^* → SiO ₂ + by-product (substrate surface reaction) Furthermore, adsorbed molecules on the surface move and desorb simultaneously. However, in a temperature range of 200 ° C. or lower, the desorption reaction is small, and thus the deposition rates of both with and without the mesh show a constant value.

FIG. 7 shows the relationship between the substrate temperature and the hardness of the substrate surface on which the SiO ₂ film was deposited with and without the mesh. As the substrate temperature increased, the hardness increased with and without the mesh. This is presumably because the coarse and dense film and the precursor adsorbed on the substrate surface were desorbed by the heating of the substrate, and therefore the deposited film was densified. The hardness of the film deposited using the mesh shows a higher value than that without the mesh. This is probably because damage to the deposited film due to electrons and ions was reduced by using the mesh. FIG. 8 shows the relationship between the substrate temperature and the adhesion strength of the SiO ₂ film deposited on the Si substrate surface. The adhesion strength of the film deposited without using a mesh is
The temperature rises significantly in a substrate temperature region of 200 ° C. or higher. This is considered to be because the film and the precursor adsorbed with weak adhesion were desorbed by the heating of the substrate. However, an increase in the adhesion strength of the film deposited using the mesh is hardly observed. This is presumably because the deposition time was shortened by using the mesh, and the desorption reaction of the film having low adhesion on the substrate surface due to thermal energy was reduced. From such a result, it is understood that when a mesh is used, a preferable temperature range is 150 to 300 ° C, and more preferably 150 to less than 200 ° C.

[0021]

As is apparent from the above description, according to the present invention, a step coverage characteristic having a good gap fill characteristic is provided, a film deposition temperature is reduced, and H in the film is reduced.
₂ O, -OH, C, etc. can be reduced to obtain a high quality film with high reliability, and in particular, a high film deposition rate, high adhesion of the film, and high hardness of the film can be obtained. A method for forming an SiO ₂ insulating film by plasma CVD as described above is provided. The film obtained by the method of the present invention is an interlayer insulating film or a protective film of fine Al wiring of an LSI (semiconductor integrated circuit), a hard coat of any other material (metal, ceramic, plastic), a friction / abrasion film or corrosion resistance. It can be applied to conductive films and the like.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an embodiment of an ECR plasma CVD apparatus used in the present invention.

FIG. 2 is a graph showing a relationship between Vickers hardness and dynamic hardness.

FIG. 3 is a graph showing a relationship between a film deposition rate and a microwave output.

FIG. 4 is a graph showing a relationship between dynamic hardness and microwave output.

FIG. 5 is a graph showing the relationship between adhesion strength and microwave output.

FIG. 6 is a graph showing a change in a deposition rate with respect to a substrate temperature.

FIG. 7 is a graph showing a relationship between dynamic intensity and substrate temperature.

FIG. 8 is a graph showing a relationship between adhesion strength and substrate temperature.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 plasma generating chamber 2 magnetic coil 3 microwave inlet 4 sample chamber 5 plasma generating gas inlet 6 inlet 7 Si <100> base material 13 supply line 16 plasma stream 17 cooling water supply port 18 cooling water discharge port

Claims (3)

[Claims] In a method of forming an SiO ₂ thin film by plasma CVD, a magnetic field is applied to a plasma generation chamber by a magnetic coil disposed around the plasma generation chamber to apply a magnetic field.
A microwave of 0 to 200 W is introduced into the plasma generation chamber,
Upstream gas is introduced into the plasma generation chamber and
A CR plasma is generated, a raw material is vaporized downstream to generate a supply gas, the supply gas is supplied from an inlet, and further, between the inlet and the substrate or between the plasma generation chamber and the inlet. Forming the SiO ₂ thin film by plasma CVD, wherein the ECR plasma is passed through a mesh provided between the substrates and the substrate is not heated, thereby depositing an SiO ₂ film on the substrate surface. Method. _{2. A} method of forming an SiO ₂ thin film by plasma CVD, wherein a magnetic field is applied to a plasma generation chamber by a magnetic coil disposed around the plasma generation chamber, microwaves are introduced into the plasma generation chamber, and upstream gas is supplied. It is introduced into a plasma generation chamber to generate ECR plasma, vaporizes the raw material downstream to generate a supply gas, and supplies the supply gas from an inlet, and further, between the inlet and the substrate or the plasma The ECR plasma is passed through a mesh installed between the generation chamber and the inlet, and the substrate temperature is heated to 150 to 300 ° C., whereby an SiO ₂ film is deposited on the substrate surface. SiO ₂ thin film forming method by plasma CVD. 3. A SiO ₂ thin film forming method by plasma CVD according to claim 2, the substrate temperature is characterized in that so as to heat below 200 ° C. 0.99 ° C. or higher.