JPH0425128A - Formation of insulating film - Google Patents

Abstract

PURPOSE:To enable the title insulating films in excellent step coverage and flatness to be formed by a method wherein the insulating films are to be multilayer structured i.e. the first layer is formed by feeding lower RF power while the second layer or later are formed by feeding higher RF power and the final layer is formed by additionally feeding Ar gas. CONSTITUTION:The title insulating films are to be formed of multilayer structured insulating films comprising respective insulating layers i.e. the first layer 15 is formed by feeding lower RF power to a specimen base while the second layer 16 or later are formed by feeding higher RF power and the final layer 17 is formed by additionally feeding Ar gas to a plasma production chamber. That is, the insulating films are multilayer structured while the first layer 15 is formed using relatively lower RF power so that a thin film in relatively soft film quality filling the role of relieving the stress on a wiring 22 may be formed. On the other hand, the second layer or later are formed using higher RF power to form the multilayer insulating films in high denseness while the final layer 17 is formed by additionally feeding Ar gas thereby enabling a flat film to be formed by the etching action of Ar gas. Through these procedures, in the insulating films in excellent step coverage and flatness and hardly doing damage to the wiring 22 can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses an ECR plasma CVD apparatus to coat the uneven surface of a substrate surface due to M wiring, etc., and fill in the depressions to form a flat interlayer insulating film or surface protection. The present invention relates to a method for forming an insulating film when forming a film.

[Conventional technology]

Normally, interlayer insulating films and surface protective films in semiconductor integrated circuits are produced using thermal
They were formed using the VD method or the high-frequency plasma CVD method, which generates a high-frequency glow discharge of raw material gas under reduced pressure to decompose the gas and form a thin film on the substrate, but in recent years, integrated circuits have become smaller and more dense. With the advancement of technology, the wiring spacing and wiring width are shifting from microns to submicrons, and ECR plasma CVD equipment is being developed as an equipment that can cope with the formation of insulating films by the CVD method. An ECR plasma CVD apparatus includes a plasma generation chamber into which microwaves are introduced and which is surrounded almost coaxially by an excitation solenoid, where the introduced gas is turned into plasma by the resonance effect of the microwaves and the magnetic field created by the excitation solenoid; It is equipped with a reaction chamber that communicates with the production chamber and is equipped with a sample stage on which a substrate is placed.In recent years, in order to improve film quality and form a flat insulating film, etc. Furthermore, the sample stage is equipped with RF power (RF means a frequency of several tens of kilometres to several tens of former Iz, usually 13.56 MHz).
A device equipped with an RF power supply that supplies RF power (used for The plasma is activated by the plasma that moves into the reaction chamber, and a thin film is formed on the surface of the substrate. Furthermore, a second excitation solenoid (hereinafter referred to as a sub-solenoid) is disposed coaxially with the excitation solenoid and at a position in the axial direction sandwiching the board, so that the sub-solenoid generates a magnetic field in a direction opposite to that of the excitation solenoid. When current is applied, both magnetic fields rapidly expand outward near the substrate.

Cusp magnetic field type ECR plasma CV that forms a so-called cusp magnetic field and makes the thickness distribution of the thin film formed on the substrate uniform.
The use of D devices is becoming more popular.

In this way, in the ECR plasma CVD apparatus, the plasma generation section and the reaction section are separated, and the plasma that moves from the high temperature plasma generation chamber to the low temperature reaction chamber activates the reactive gas introduced into the reaction chamber. Since a thin film is formed on the surface, low-temperature film formation is possible, and high-activity, high-density plasma can be obtained at low gas pressure, as well as film formation with excellent density and acid resistance based on low gas pressure. is possible.

Also, when RF power is supplied to the sample stage 1 and therefore the substrate,
A negative potential is generated on the substrate surface due to the difference in mobility between electrons and ions in the RF plasma generated on the substrate surface, and the film is further densified due to ion bombardment on the substrate surface due to this negative potential. For example, when forming a silicon oxide film as an insulating film on an uneven surface, the film extending horizontally from the top surface of the convex portions on the uneven surface is removed by etching with 0□ gas ions, and the film is deposited with the concave portions open. A step film with uniform thickness and quality can be obtained on the surface.

Furthermore, by supplying additional metering gas to the plasma generation chamber, and utilizing the strong etching effect of the generated row gas ions, the growth rate of the film on the top surface of the convex part, where the surface electric field is high, is lower than that of the concave part, while flat insulation is achieved. A film can be formed. In the case of the above-mentioned cusp magnetic field type plasma CVD apparatus, the amount of electrons reaching the substrate is reduced due to the shape of the magnetic field lines that form the cusp magnetic field (ions have a larger mass than electrons and reach the substrate due to their inertia). Since the surface potential of the substrate becomes smaller, the supplied RF power is increased to maintain the desired negative potential.

(Problem to be solved by the invention) However, when the insulating film formed on the uneven surface due to wiring etc. is, for example, a silicon nitride film, the N2 gas ion etching of the film that extends in the lateral direction of the top surface of the protrusion The effect is that the 02 gas ions in the silicon oxide film are not very large, and as a result, the film is formed without removing the overhang in the lateral ζ direction on the top surface of the convexity, resulting in the film on the sidewall of the convexity lacking in density, as shown in Figure 14 ta+. As shown in FIG.
There was a problem in that a cavity was generated on the way to planarization as shown in FIG.

Therefore, if the RF power is increased to enhance the etching effect of N2 gas ions, hillocks may occur due to ion bombardment, or the temperature of the uneven surface may increase due to the ion bombardment, resulting in a decrease in the coefficient of thermal expansion between the wiring and the insulating film. Disconnection occurs due to the difference. In addition, the unevenness of the film thickness distribution and film quality distribution due to the unevenness of the electric field distribution on the uneven surface increases.
Stress in the film due to this non-uniformity is transmitted to the wiring, resulting in disconnection due to so-called stress migration.

The purpose of this invention is to obtain uniformity in film thickness distribution and film quality distribution even if a film is formed on an uneven surface while supplying RF power to a sample stage, and to achieve one-step film quality and flatness that prevent damage to wiring. An object of the present invention is to provide a method for forming an excellent insulating film.

[Means to solve the problem]

In order to solve the above problems, in the present invention, the insulating film has a multilayer structure in which each layer is an insulating film, and the first layer reduces the RF power supplied to the sample stage, and the second layer Thereafter, an insulating film forming method will be used in which the RF power is increased and the final layer is formed by additionally supplying Δr gas to the plasma generation chamber.

[Effect]

In this way, by forming the insulating film into a multilayer structure and forming the first layer using a relatively low FIF power, we can create a thin film with a relatively soft film quality that has the effect of relieving the stress that is transmitted to the wiring. is formed and the film is thin, so even if the first layer is a silicon nitride film, the lateral protrusion of the film on the top surface of the wiring is small, and the film quality on the wiring sidewalls is affected by the top surface and the bottom of the trench. There is not much difference compared to the membrane,
A discontinuous line is less likely to occur between the side wall film and the bottom film. Furthermore, since the RF power is small, it becomes difficult to generate hillocks due to ion bombardment. By forming the second and subsequent layers using higher RF power, a multilayer insulating film with high density is formed over the entire surface of each of the second and subsequent layers.

Furthermore, since the insulating film of each layer can be formed by arbitrarily selecting any of the S10 film, SIN film, or 5iON19, it is possible to obtain a multilayer insulating film having desired characteristics by appropriately combining these films. can. When forming the final layer, ^r gas is additionally supplied into the plasma generation chamber, so the strong etching action of the metering gas ions removes one part of the multilayer film formed just before the final layer.
There is a difference between the ratio of etching rate and film formation rate in the convex part where the electric field strength is high and that in the concave part where the electric field strength is low. A flat film is formed while being buried in the pores.

In this way, the insulating film is formed as a multilayer insulating film in which the RF power during the formation of each layer is changed, and additional gas is supplied into the plasma generation chamber during the formation of the final layer. It is possible to form a dense film as a whole while preventing the occurrence of thermal and mechanical disconnection of wiring. In the step film, since the first N mechanically shields the wiring by 5 m, it is possible to increase the RF power from the second layer onward to obtain a uniform film thickness and quality.
The subsequent planarization requires only the additional supply of Ar gas, and by simply changing the type of gas supplied to the plasma generation chamber, a high-quality insulating film that does not damage the wiring can be created. It can be easily formed.

〔Example〕

FIG. 3 shows an EC to which the insulating film forming method according to the present invention is applied.
An example of the configuration of an R plasma CVD apparatus is shown.

This device includes a microwave source (not shown), a waveguide 1 that transmits the microwaves oscillated by the microwave source, and a plasma generation chamber 5 into which the microwaves that have passed through the waveguide 1 are introduced.
The atmospheric pressure on the waveguide 1 side and the vacuum on the plasma generation chamber 5 side are isolated. A microphone 1 wave introduction window 2 made of a dielectric material,
The excitation solenoid 4 surrounds the plasma generation chamber 5 substantially coaxially and communicates with the plasma generation chamber 5 through an opening 5 a at the lower end of the plasma generation chamber 5 . A reaction chamber 6 equipped with a sample stage 10 on which a film-forming substrate 9 is placed, a sub-solenoid arranged coaxially with the excitation solenoid 4 on the back side of the sample stage 10, and a The main components are an RF power source 12 that supplies RF power, and a variable capacitor 13 that adjusts the RF power supplied to the sample stage 10. The plasma generation chamber 5 is formed as a cavity resonator that forms a desired resonance mode of microwaves, and microwaves are introduced from the microwave source while a gas having a film component such as 0□+NZ is introduced from the first gas introduction system 3. At the same time,
The current flowing through the excitation solenoid 4 is adjusted to create a magnetic flux density that resonates with the microwave in the plasma generation chamber 5 (the frequency of the microwave is set to the industrially used standard frequency of 2.45 GHz).
In this case, a magnetic field region having a magnetic field strength of 875 Gauss) is formed, and high-density plasma is formed in the plasma generation chamber 5.

This plasma was introduced into the reaction chamber 6 from the second gas introduction system 7 through the opening 5a along the magnetic lines of force formed by the excitation solenoid 4. The reactive gas S i H4 (silane) having a film component is decomposed by plasma energy while heading toward the sample stage, and the cuspid magnetic field region formed near the substrate 9 by the excitation solenoid 4 and the sub-solenoid 11 is used to decompose the reactive gas S i H4 (silane) in the plasma. Many of the electrons head toward the peripheral wall of the reaction chamber along the lines of magnetic force forming the wall cusp magnetic field, and many of the ions bend their direction together with the electrons until they reach the substrate 9 with their large inertia. From the shape of the cusp magnetic field,
Since the curvature in the moving direction of ions is larger near the axis of the substrate and smaller near the periphery, the in-plane distribution of ion density reaching the substrate is different from that of the excitation solenoid 4 without sub solenoid 11.
Compared to when the plasma moves along the divergent magnetic field caused by the magnetic field alone, it is averaged to a greater extent, and a uniform film thickness distribution can be obtained on the substrate. The ECR plasma CV configured in this way will be explained below.
An embodiment of this method will be described in which a flat insulating film is formed on an uneven surface of a substrate due to wiring by the insulating film forming method of the present invention using apparatus D. Note that in the multilayer insulating film according to the present invention, each layer is formed as an insulating film of either SiO film, SiN film, or 5iNO film, and two layers in contact with each other do not need to have different compositions.

FIG. 1 shows, as a first embodiment of the present invention, the process of forming an insulating film by the insulating film forming method of the present invention in the case where the insulating films of each layer constituting the insulating film have different compositions. be. The insulating film had a three-layer structure, and the film formation conditions were as follows.

(1) RF power when forming the first layer film 15 is 0 to 200W.
The film thickness will be 1,000 to 2,000 people.

(2) RF power when forming the second layer film 16 is 400 to 75
It is assumed to be 0W.

(3) RF power when forming the third layer film 17 is 400 to 75
At the same time as setting the power to 0W, Ar gas was added to the plasma generation chamber at 10W.
~11005CC (cc/m when converted to standard condition)
Additional supply is made at a flow rate of 1n).

Common to each of the above items, (a) Microwave power is set to 300 to 1400W.

Tb) Increase the gas pressure inside the device to 5 x 10-3 to I x 1
0-'Torr.

(C) Gas flow rate ratio: 5itlt10□-0,3~0.
8SiHt/NZ = 0.5 ~ 1.2SiH, 10
□+N2=0.3 to 1.0.

When the insulating film is formed under the above film forming conditions, the insulating film constituting the first layer is formed using a low RF power of 0~200W, so the activation of the wiring pattern surface that 0□ plasma or N2 plasma has While maintaining the cleaning effect,
Hillock formation on the wiring pattern surface and thermal disconnection of the wiring due to ion bombardment by ions in the plasma are prevented.
In addition, the film is soft and has the effect of mitigating stress migration, and can protect the wiring from mechanical disconnection even if stress transfer occurs from the dense film formed in the second layer or later. In addition, since the film is thin, the lateral overhang of the film deposited on the top surface of the wiring is small, and the film on the side wall of the wiring has a film quality that is not much different from the film on the bottom of the trench, and there is a discontinuous line between the two. This makes it less likely that wiring will be eroded during subsequent etching.

Since the second layer is formed with increased RF power, it has precise and desired characteristics. It is formed as an insulating film with uniform thickness and quality.

The third layer is formed by increasing the RF power and supplying additional measuring gas to the plasma generation chamber, so the strong etching action of the Ar plasma etches the top of the wiring where the electric field is strong, as shown in Figure 1 fc). Film formation progresses while etching the second layer in a tapered shape facing the edge of the surface. At this time, the electric field strength at the bottom of the trench is smaller than that at the top of the wiring, so the film grows faster than at the top, and by controlling the RF power to an appropriate level, it is possible to form a flat film while filling the trench. .

Figure 2 shows the structure of an insulating film when the film formation conditions are the same as in Figure 1, and each layer has the same composition. The cross-section of the step coating shown in FIG.
A cross section of is shown.

〔Effect of the invention〕

As described above, in the present invention, the flat insulating film formed on the uneven surface due to the wiring on the substrate is an insulating film with a multilayer structure in which each layer is an insulating film, and the first
The layers are formed using a low RF power supplied to the sample stage, the second and subsequent layers are formed using a higher RF power, and the final layer is formed by an insulating film formation method in which bamboo gas is additionally supplied to the plasma generation chamber. Therefore, we decided to form a dense film by simply changing the type of gas introduced into the plasma generation chamber while preventing hillock formation on the wiring surface and thermal and mechanical disconnection of the wiring. I can do it. In addition, the high RF power for the second and subsequent layers makes it possible to form a uniform step coating with a film thickness of 1, and the subsequent flattening of the step coating is achieved by additionally supplying Ar gas to the plasma generation chamber, and by increasing the amount of ^r gas ions. This method was made possible by utilizing the strong etching action and the difference in etching speed caused by the difference in electric field between the uneven surfaces.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the process of forming an insulating film by the insulating film forming method of the present invention in the case where each layer of the insulating film constituting the insulating film has a different composition. The process of forming an insulating film is divided into the stage of completing the step coating ((a) in the same figure) and the stage of completing the flattening ((b) in the same figure) in the case where each layer of the insulating film constituting the insulating film has the same composition.
), FIG. 3 is a longitudinal sectional view showing an example of the configuration of an ECR plasma CVD apparatus to which the insulating film forming method of the present invention is applied, and FIG. 4 shows the conventional insulating film forming method. S
Stage of completion of step coating when using iN film (Figure (a))
FIG. 4 is an explanatory diagram showing a stage in the middle of planarization (FIG. 3(b)). 4: Excitation solenoid, 5: Plasma generation chamber, 6: Reaction chamber, 9: Substrate, 10: Sample stage, 12: RF power supply, 15: First layer film (first layer), 16: Second layer film (first layer). 2 layers), 17:
3rd layer film (final layer), 21: Insulating film, 1st side Fig. 2

Claims (1)

[Claims] 1) A plasma generation chamber into which microwaves are introduced and surrounded almost coaxially by an excitation solenoid, and where the introduced gas is turned into plasma by the resonance effect of the microwaves and the magnetic field created by the excitation solenoid, which communicates with the plasma generation chamber. An ECR equipped with a reaction chamber equipped with a sample stage on which a substrate is placed, and an RF power source that supplies RF power to the sample stage.
Using a plasma CVD device, while supplying RF power to the sample stage, the reactive gas introduced into the reaction chamber is activated by plasma that moves from the plasma chamber to the reaction chamber along the magnetic field lines created by the excitation solenoid, and the substrate surface is A method for forming a flat insulating film on an uneven surface due to wiring, etc., wherein the insulating film is a multilayered insulating film in which each layer is an insulating film, and the first layer is The RF power supplied to the sample stage is small, the second and subsequent layers are formed with a larger RF power, and the final layer is formed using Ar in the plasma generation chamber.
A method for forming an insulating film, the method comprising forming an insulating film by additionally supplying a gas.