JP2913672B2 - Insulating film formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulating forming method for forming an insulating thin film on a substrate. The present invention can be used, for example, in a manufacturing process of forming a thin film on a semiconductor substrate to obtain an LSI or other semiconductor device.

SUMMARY OF THE INVENTION The present invention provides a method for forming a first thin film on a substrate by a plasma CVD method and continuously forming a second thin film on the first film by an ECR plasma CVD method. First on
By interposing the thin film described above, the adhesion between the substrate and the thin film is improved, and the shoulder of the step is not scraped during the formation of the second thin film.

[Conventional technology]

In recent years, in the field of electronic materials, particularly semiconductor devices, further miniaturization and integration of devices have been demanded.

For example, in the case of LSI, the pattern size is further reduced by miniaturization. With this reduction, the wiring width becomes narrow and the interval becomes narrow.

However, the thickness of the wiring cannot be reduced to avoid an increase in wiring resistance. As a result, in a fine wiring, for example, a submicron wiring, the aspect ratio becomes as high as 1.0 or more. Therefore, it is necessary to bury a high-quality insulating film between the submicron wires having a high aspect ratio and to planarize the insulating film surface.
This is an issue for thin film formation technology in the submicron age.

Meanwhile, in recent years, as a new thin film formation and planarization technology, EC
A bias ECRCVD method combining R plasma CVD and sputtering on a substrate has been developed, and various proposals have been made.

The ECR plasma CVD method is a technique for forming a film on a substrate by plasma using plasma excited by electron cyclotron resonance (ECR) by microwaves (ECR plasma CVD).
For the method, see, for example, the description of JP-A-60-115235).

[Problems to be solved by the invention]

However, the conventional technology using the ECR plasma CVD method includes:
There is a problem in the adhesiveness between the thin film thus obtained and the base. That is, the thin film thus formed is liable to peel off from the base. In particular, this problem is remarkable when the material is deposited on a base having a property different from that of the deposit. For example, when forming a SiO ₂ film on the silicon surface and flattening it,
It is a big problem. The formation of SiO ₂ on such a silicon surface is actually required when filling a relatively shallow trench called a shallow trench by bias ECRCVD.
In this case, the above problem occurs.

Furthermore, in the case of embedding SiO _{2 in} the shallow trench on silicon, there arises a problem that the shoulder of the groove is etched by the bias ECRCVD method.

In other words, the bias ECR plasma CVD technique forms a flattened film by simultaneously performing deposition and etching. To form a flat film, a bias is applied (actually, an RF bias is generally used. In the case of depositing SiO ₂ in the Si trench 1b of the silicon substrate 1a as shown in FIG. 5, if an attempt is made to fill the SiO ₂ by applying an RF bias from the beginning, The shoulders (parts indicated by reference numeral 2a with hatching in FIG. 6) are etched, resulting in the shape as indicated by reference numeral I in FIG. In FIG. 6, what is denoted by reference numeral 2b with fine dots is the deposited SiO ₂ .

Even if a thermal oxide film is formed on the inner wall of the Si trench 1b,
A similar problem arises because the film thickness cannot be too large.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems, maintain the advantages of the ECR plasma CVD method, and achieve good adhesion with a base, and the like. ECR plasma C that can form a thin film that is unlikely to cause cracks and that does not remove the shoulder of the step even if it is used to form a thin film for filling steps such as trenches
An object of the present invention is to provide a method for forming an insulating film using a VD method.

[Means for solving the problem]

The insulating film forming method of the present invention is an insulating film forming method for forming an insulating film on a substrate having a step, wherein the first insulating film (hereinafter appropriately referred to as the first insulating film) is formed on the substrate by a plasma CVD method in a plasma processing chamber. (Sometimes called a thin film)
Is formed, and then the substrate is moved to an ECR plasma processing chamber, and a second insulating film (hereinafter sometimes referred to as a second thin film as appropriate) is continuously formed on the first insulating film by an ECR plasma CVD method. This solves the above problem.

In the present invention, plasma CVD for forming a first thin film
As a method, a normal plasma CVD method may be used, or an ECR plasma CVD method may be used without applying a bias.

In the former case, a substrate, for example, a semiconductor substrate is held in a plasma generation chamber and a first thin film is formed here, and then the substrate is moved from the plasma generation chamber to a bias ECRCVD processing chamber.
Here, it can be implemented to form a second thin film. This can be done in the same ECR device. In the former case, the first thin film can be formed by high-energy plasma.

In the latter case, the bias ECRCVD apparatus can be used to form the first thin film by reducing the RF bias applied power to zero, and then apply the RF bias applied power to form the second thin film.

In either case, the method can be used as a method for forming a flattening film for filling the trench. In this case, the film can be formed on the inner wall of the trench with the first thin film, and the trench can be filled with the second thin film. .

(Operation)

According to the present invention, the first substrate is formed on the substrate by the plasma CVD method.
Is formed, the adhesion between the substrate and the first thin film is good, and the film does not peel off.

In addition, since the second thin film is formed after the formation of the first thin film, even if a bias is applied in the formation of the second thin film, the first thin film functions as a buffer layer, and the film is formed on the trench. In this case, the shoulder of the trench can be prevented from being cut.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, needless to say, the present invention is not limited by the following examples.

Embodiment 1 In this embodiment, the present invention is embodied in forming a thin film in a manufacturing process of a highly integrated SRAM.

In this embodiment, in the same bias-applicable ECR plasma CVD apparatus, first, a substrate 1 is arranged as shown in FIG. 1 to form a first thin film by a plasma CVD method. As shown in the figure, a second thin film was continuously formed by changing the position of the substrate 1 by the bias ECRCVD method.

That is, in this embodiment, the plasma EC shown in FIG.
A substrate 1 to be processed (a silicon wafer in this example) is held in a plasma generation chamber 11 of an RCVD apparatus 10, and a first thin film is formed on the substrate 1 by a plasma CVD method. In this example,
The first thin film functions as an adhesive layer for improving the adhesion to the substrate. Therefore, it is preferable to increase the adhesiveness by performing CVD using high-energy plasma. In the plasma CVD, a bias may or may not be applied, and a magnetic field may or may not be applied.

Specifically, as the first thin film, silane was used as a reactive gas system, and an SiO ₂ thin film was formed on the silicon surface of a silicon wafer as the substrate 1. Here, a SiO ₂ thin film having good adhesion to the silicon surface was obtained.

Thereafter, the wafer as the base 1 is removed from the plasma chamber 11 by EC.
The substrate is transferred to the R processing chamber 12, and is placed at the position of a normal bias ECRCVD method, where deposition is performed by the bias ECRCVD method to form a second thin film. Thereby, flattening is performed.
In this example, the position of the substrate 1 is changed by moving the stage 2 supporting the substrate 1 from the position shown in FIG. 1 to the position shown in FIG. Since the second thin film was formed, continuous film formation was easily performed.

The above movement of the substrate 1 was performed through the plasma extraction window 13 of the ECR device 10. However, the commercially available ECR device has a plasma extraction window 13 of about 10 cm.
May be smaller than the diameter of the wafer, but in this case, the plasma extraction window is required to allow the base 1 to move.
You can add a system to enlarge or remove 13. Thus, the present embodiment can be used using a commercially available device.

In forming the second thin film, a magnetic field is applied by the magnet coil 14 and ECR plasma CVD is performed by applying a microwave schematically indicated by an arrow 15, whereby a thin film without damage is obtained. If the growth of the thin film is continued only in the plasma generation chamber 11, damage may occur. However, there is no problem in the step of forming the second thin film. Also, EC
By performing deposition and etching simultaneously, which are peculiar to the R plasma CVD method, a film having excellent flatness can be obtained. However, when forming the second thin film, a bias is always applied (can be applied by an RF power supply indicated by 16 in the figure)
do not have to. Reference numeral 17 schematically indicates a plasma flow at the time of forming the second thin film.

As described above, a film having good adhesion and good coverage is formed.

The second thin film may be SiO ₂ , or may be formed of SiN (silicon nitride) or aluminum oxide or nitride by appropriately selecting a reaction gas (these materials are the first thin film). It can also be used for formation).

In the case of filling the trench, the present embodiment can achieve good filling of the hole, but in the case of the illustrated example, the filling efficiency is particularly good because of the directionality (the direction in which the deposit grows in the filling direction).

In the above example, the first and second thin films are formed in the same ECR plasma CVD apparatus. However, it is a matter of course that the first and second thin films may be formed in different apparatuses.

Example 2 This example uses the present invention in an SRAM manufacturing process,
First, a thin first film is formed on a substrate by using an ECR plasma CVD apparatus under a condition in which no bias is applied (non-bias), and then a second thin film is formed under a bias application condition.

In this example, the first thin film was formed under the following conditions.

Working gas and flow rate: SiH ₄ = 24 SCCM, O ₂ = 40 SCCM Microwave: 800 W Applied bias: 0 W Pressure: up to 5 × 10 ⁻⁴ Torr Under the above conditions, a 50-500 Å SiO ₂ film is formed on a Si substrate. The resulting structure is shown schematically in FIG. In the figure, 1a is a Si substrate as a base, 1b is a trench, and 1c is a non-biased SiO ₂ film as a first thin film.

 Next, a second thin film was formed under the following conditions.

Working gas and flow rate: SiH ₄ = 24 SCCM, O ₂ = 40 SCCM Microwave: 800 W Applied bias: 300 W Pressure: up to 5 × 10 ⁻⁴ Torr The SiO ₂ film is formed under the above-described bias application conditions. At this time, a condition for adding a rare gas such as Ar to improve the planarization efficiency may be used. As a result, as shown schematically in FIG. 4, a smooth and flat second thin film 1d was obtained. In fact, the flatness was good.

In the present embodiment, the first thin film 1c exhibits a buffer action as a buffer layer when the second thin film 1d is formed.
In the flattening step of forming the thin film 1d, the shoulder of the trench 1b of the silicon substrate as the base 1 is not etched. Furthermore,
Adhesion between the non-bias -SiO ₂ film is a silicon surface and a first thin film 1c of the substrate 1 is good, also, bias application -SiO ₂ is the non-bias -SiO ₂ film and the second thin film 1d
Since the adhesion of the film is also good, in this embodiment, a bias-applied SiO ₂ film can be formed on the silicon substrate with good adhesion.

〔The invention's effect〕

As described above, according to the present invention, while maintaining the advantages of the ECR plasma CVD method, it is possible to form a film in which the adhesion to the base is good and the peeling-off is unlikely to occur, and the step such as a trench is buried. This has the effect that a thin film in which the shoulder of the step is not removed by etching can be formed even when it is used for forming a thin film for use.

[Brief description of the drawings]

1 and 2 are diagrams showing the formation of the first and second thin films in Example-1. 3 and 4 are diagrams showing the formation of the first and second thin films in Example-2. 5 and 6 are diagrams for solving the problems of the prior art. 1, 1a: base, 1c: first thin film, 1d: second thin film,
10 ... ECR plasma CVD equipment.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 16/00-16/56 H01L 21/205, 21/31

Claims (1)

(57) [Claims] 1. An insulating film forming method for forming an insulating film on a substrate having a step, comprising: forming a first insulating film on a substrate by a plasma CVD method in a plasma processing chamber;
Forming an insulating film, and then moving the substrate to an ECR plasma processing chamber, and continuously forming a second insulating film on the first insulating film by an ECR plasma CVD method.