JPH03191069A - Method and device for forming thin film - Google Patents

Abstract

PURPOSE:To improve step coverage and to form a film without occurring any short circuit and disconnection in the device for irradiating a substrate to be coated with the film with a plasma current in high vacuum by providing a rotating mechanism and an inclining mechanism to a substrate holder arranged in a film forming chamber. CONSTITUTION:A microwave power is supplied to a discharge chamber 1 to convert gaseous oxygen supplied to the chamber 1 into plasma, and the oxygen plasma is transported to a substrate 3 to be coated with a film. Gaseous silane supplied to the film forming chamber 2 is decomposed in the process to form an SiO2 thin film on the substrate 3. In this device, a turning rate varying mechanism 16 and an inclination varying mechanism 17 are provided to the supporting shaft of the holder 4. The substrate 3 is rotated by the mechanism 16, the inclination theta of the substrate 3 to the plasma current 12 is changed, and a film is formed. As a result, a film is formed even on the step of the substrate 3 with good step coverage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thin film forming apparatus and method for forming a film by irradiating a film forming substrate with a plasma stream at a degree of vacuum of 10 −3 or higher.

BACKGROUND ART As a conventional technique for forming a thin film in a high vacuum of 10-3 to 10-'l, there is a CVD apparatus using electron cyclotron resonance. This method decomposes a reactive gas using electron cyclotron resonance plasma generated by microwave power and a resonant magnetic field in a discharge chamber, and forms a thin film by irradiating a plasma flow containing the decomposed gas onto the substrate to be deposited. It is.

An example of forming a SiO□ thin film using this conventional method will be described. In FIG. 7, microwave power supplied from a microwave generating means (not shown) is supplied to the discharge chamber 1 from a waveguide 6 through a ceramic window 5 for sealing the vacuum, and The oxygen gas supplied from the oxygen supply lower to the discharge chamber 1 is turned into plasma by the resonance magnetic field of the solenoid 10. This oxygen plasma is solenoid 10
The silane gas supplied from the deposition gas supply port 8 is decomposed on the way, so the deposition substrate 3 does not contain the decomposed silane gas. A plasma stream is irradiated, and a 5iOz thin film is formed on the film-forming substrate 3.

This method is an excellent technique that can form not only SiO□ thin films but also high-quality thin films at high speed without heating the film-forming substrate 3.

Problems to be Solved by the Invention However, in the conventional example described above, there is a problem in that step coverage is poor due to the high degree of vacuum during film formation, and therefore various problems occur when forming a film on a portion with a step difference.

As an example, we will explain the case where the upper and lower wiring lines 13 and 14 that intersect on the film-forming substrate 3 are insulated with another 0□ thin film 15 as shown in FIG. After forming the wiring 13, SiO
When the □ thin film 15 is formed, the SiO □ thin film 15 is interrupted as shown in FIG. 3(a) due to poor step coverage.
As shown in part A shown in a), the lower wiring 13 and the upper wiring 1
4 is short-circuited, or the wiring 14 is broken as shown in section B shown in FIG. 3(b). Therefore, the above-mentioned conventional technique has a serious problem in that it cannot be applied to film formation on areas with steps.

Means for Solving the Problems In order to solve the above-mentioned problems, a thin film forming apparatus according to the present invention is provided with a discharge chamber for generating plasma.
A substrate holder for installing a substrate to be film-formed is arranged in a film-forming chamber evacuated to a vacuum level of 1.5-1 or higher, and the substrate holder is provided with a rotating mechanism and a mechanism for variably tilting with respect to the plasma flow.

Further, the thin film forming method of the present invention uses the thin film forming apparatus described above, in which the film forming process is performed while rotating the film forming substrate and changing the inclination angle of the film forming substrate with respect to the plasma flow. It is. In this thin film forming method, the plasma flow is 1/co
It is preferable to configure the irradiation time to be proportional to sθ.

A working thin film forming apparatus generally uses microwaves supplied to a discharge chamber and a magnetic field generator installed around the discharge chamber to turn the gas supplied into the discharge chamber into plasma by electron cyclotron resonance, and forms a film along the lines of magnetic force caused by the magnetic field. It irradiates the chamber and forms a film on the substrate to be film-formed installed in the film-forming chamber.
In film deposition equipment with a high degree of vacuum, which is evacuated to a vacuum level of 0-3 Torr or more, the free path of the deposition particles is long and the straightness is high, so it is necessary to fix the deposition substrate with stepped parts such as wiring. When plasma is irradiated in this state, deposition particles increase on the surface facing the plasma flow, but there is less deposition on the surface that is inclined to the plasma flow, resulting in uneven film formation and poor step coverage. It becomes a membrane.

Since the thin film forming apparatus of the present invention can variably tilt the substrate holder on which the substrate to be film-formed is placed with respect to the plasma flow direction, a thin film can be formed on the side surface of a step on the substrate to be film-formed. In addition, by making the irradiation angle of the plasma stream variable, it is possible to equalize the amount of deposition between the side surface of the stepped portion and the other surface. Furthermore, since the thin film forming apparatus of the present invention is equipped with a mechanism for rotating the substrate holder, it is possible to irradiate the entire side surface of the stepped portion with the plasma flow, and to remove the shadowed portion that is not irradiated with the plasma flow. can be eliminated from existence. As described above, according to the thin film forming apparatus of the present invention, an average amount of plasma irradiation can be applied to the entire film forming surface by controlling the tilt angle and rotation speed.

Since the thin film forming method of the present invention uses the above-mentioned apparatus, it can perform the above-mentioned functions, and furthermore, the film-forming substrate is constantly rotated and the inclination angle is changed as the film-forming process progresses. Therefore, it is possible to form a uniform film on the substrate in the most natural state. In particular, while changing the irradiation angle with respect to the plasma flow from 90 degrees to 0 degrees, the plasma irradiation time is set to 1 depending on the irradiation angle θ.
/cos θ, it is possible to compensate for the fact that depending on the irradiation angle, the amount of irradiation per unit area of the substrate to be film-formed decreases in proportion to l/cos θ of the irradiation angle θ. A film of uniform thickness can be formed on the substrate.

One specific method is to slow down the rotation speed to lengthen the irradiation time for the plasma flow when the tilt angle is large, and to increase the rotation speed to shorten the irradiation time for the plasma flow when the tilt angle is small. There is a method of forming a film uniformly on each surface of a substrate to be film-formed.

Embodiments An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment, and the same elements as those of the conventional example are given the same reference numerals and the explanation thereof will be omitted.

The difference between this embodiment and the conventional example is that the substrate holder 4 on which the film-forming substrate 3 is installed is provided with a rotation mechanism and a tilting mechanism for tilting it with respect to the plasma flow 12, so that the substrate holder 4 can be held horizontally. The discharge chamber 1 is installed obliquely with respect to the film forming chamber 2 so that it is inclined with respect to the irradiation of the plasma flow 12 even in the maintained state.

As shown in the conventional example, when the plasma flow is irradiated perpendicularly to the film-forming substrate 3, the thin film forms as shown in (a), (b), and (C) in FIG.
) and (d) in this order. This is done by applying the SiO□ thin film 15 shown in FIG.
This applies to the case where a film is formed on the wiring 13. In this way, when the plasma flow is irradiated perpendicularly to the deposition target substrate 3, the step coverage is poor because the thin film is not deposited on the side surfaces of the stepped portion, which may cause short circuits and disconnections in the wiring as described above. Become. Especially in CVD equipment that uses electron cyclotron resonance, the degree of vacuum ranges from 10-3 Torr to 10 Torr.
-' This tendency is particularly noticeable when the torque is as high as Tall, and the step coverage becomes extremely poor.

Therefore, by irradiating the deposition target substrate 3 with a plasma stream from an oblique direction, a thin film can be deposited even on the side surfaces of the stepped portions. However, even if the plasma flow is irradiated from an oblique direction while the substrate to be film-formed is stationary, the result shown in Fig. 5 (a) is
), et al.), and (C), the film is formed only on one side of the stepped portion, and no thin film is formed on the portion A shaded by the plasma flow. Furthermore, even if the plasma stream is irradiated from an oblique direction while rotating the film-forming substrate 3, shadows are created by the steps, so the amount of deposition on that part is only about half that of other parts, as shown in FIG. As shown in dl, a recess like part B occurs near the step.In the state shown in Fig. 5(d), a short circuit as shown in Fig. 3(a) does not occur, but the deposition step Figure 3 (b)
) becomes more likely to cause wire breaks as shown.

Therefore, in the present invention, the film-forming substrate + Jli 3 is rotated and the angle of irradiation with the plasma flow is made variable, so as shown in Fig. 6, step coverage is good, the deposition step is small, and wire breakage does not occur. Formation of a thin film that does not occur is achieved. Figure 6 shows the plasma flow irradiation angles θ1, θ2, θ
This figure shows the state in which a thin film is deposited when the film is deposited while changing continuously from step 3. When the irradiation angle is large as shown in Figure 6 (a), the thin film is deposited on the vertical surface of the stepped part. It is deposited only on flat surfaces, and hardly deposited on flat surfaces. When the irradiation is performed at an angle of about 45 degrees as shown in FIG. 6(b), a film is deposited on the flat surface, but a large depression is created as in the case shown in FIG. 5(d). If the irradiation angle is further reduced as shown in FIG. 6(C), the amount of deposition on the flat portion increases, the depression becomes relatively small, and a film can be formed that covers the stepped portion almost uniformly.

However, when the irradiation angle is made variable, if the irradiation angle is large, the density of the plasma flow irradiated per unit area of the film-forming substrate 3 becomes small, so the irradiation amount per unit area is It decreases approximately in proportion to 1/COSθ. Therefore, in the thin film forming method according to the present invention, in order to equalize the irradiation amount and the deposition amount regardless of the irradiation angle, a tilt angle variable mechanism and a rotation speed are used so that the irradiation time can be increased almost in proportion to l/cos θ. Controls the variable mechanism. That is, while changing the irradiation angle θ from 90 degrees to 0 degrees, the irradiation time of the plasma flow is changed l/c according to the irradiation angle θ.
It changes in proportion to osθ. For example, if the irradiation time is 1 when θ=0 degrees, the irradiation time is 1.4 times when θ=45 degrees, and the irradiation time is 5 times when θ=80 degrees.
．． 8 times. Note that the irradiation angle θ is an angle of inclination of the normal direction of the surface of the film-forming substrate 3 with respect to the direction of the plasma flow 12.

The configuration for implementing this is such that a variable rotational speed mechanism 16 and a variable tilt angle mechanism 17 are provided on the support shaft of the substrate holder 4, and each variable mechanism is controlled by a control device 18.

This embodiment is shown as a schematic configuration diagram in FIG. 1. A variable rotation speed mechanism 16 is provided on the support shaft of the substrate holder 4 on which the substrate 3 to be deposited is placed, and the substrate holder 4 is tilted at an arbitrary angle. A variable inclination angle mechanism 17 is provided.

The following two methods can be applied to this embodiment to control each variable mechanism.

First, when the rotation speed is constant, the inclination angle θ
The number of rotations per rotation is controlled in proportion to 1/cosθ. In other words, when the inclination angle θ is large, the time to maintain that angle is increased, and when the inclination angle θ is small, the time to maintain that angle is shortened (controlled).Next, when the rotation speed is made variable , the rotation speed for each inclination angle θ is 1/cosθ
control in proportion to. That is, when the tilt angle θ is large, the rotation speed is controlled to be slow (and when the tilt angle is small, the rotation speed is controlled to be fast).

In this embodiment, the rotational speed variable mechanism 16 includes a drive motor and changes the rotational speed in response to a control signal from a control device 18. The variable inclination angle mechanism 17 is a variable mechanism as shown in FIG. 1, which is driven by a drive motor 19. The control signal can be programmed into the control device in advance with optimal data according to the type of thin film formation.
Rotation speed and tilt angle can be freely linked and controlled.

Effects of the Invention According to the present invention, CVD by electron cyclotron resonance
Even when using equipment with a high degree of vacuum and a straight line of plasma flow, it takes advantage of the excellent property of being able to deposit high-quality thin films at high speed, while also eliminating steps that have traditionally had many problems. When a film is formed on a certain substrate, it is possible to form a film with good step coverage even on a portion with steps, making it possible to form a high-quality thin film without short circuits or disconnections.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an embodiment of the present invention, Fig. 2 is a perspective view showing an example of a substrate to be film-formed with steps, Fig. 3 is an explanatory diagram showing film-forming defects in the conventional example, and Fig. 4 is FIG. 5 is an explanatory diagram showing the deposition state of a film formed by plasma irradiation from a vertical direction. FIG. 5 is an explanatory diagram showing a deposition state of a film formed by plasma irradiation from an oblique direction. FIG. It is an explanatory view showing a membrane state, and a schematic configuration diagram. Figure 7 is a conventional example

Claims (3)

[Claims] (1) Deploy a discharge chamber that generates plasma 10^-^
A substrate holder for installing a substrate to be film-formed is arranged in a film-forming chamber evacuated to a vacuum level of 3 torr or more, and the substrate holder is provided with a rotating mechanism and a mechanism that variably tilts with respect to the plasma flow. Thin film forming equipment. (2) In the thin film forming method using the thin film forming apparatus according to claim 1, the film forming process may be performed while rotating the film forming substrate and changing the inclination angle of the film forming substrate with respect to the plasma flow. Characteristic thin film formation method. (3) The thin film forming method according to claim 2, characterized in that the plasma flow is irradiated for a time proportional to 1/cos θ with respect to an inclination angle θ of the normal direction of the surface of the substrate to be film-formed with respect to the direction of the plasma flow. .