JPH0791639B2 - Spatter method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin film sputter film forming technique, and in particular, it allows a film forming material to easily cover minute steps, grooves or holes on a substrate surface of a semiconductor device or the like. The present invention relates to a sputtering method for depositing.

[Conventional technology]

In the sputtering film formation technique, an attempt to increase the magnetic field of a component parallel to the target surface to increase the current flowing into the film formation target is described in, for example, JP-A-60-221563. That is, by facing the magnetron-type sputter electrode and the substrate and applying a negative bias voltage to the substrate surface, some of the ions in the plasma generated on the magnetron-type sputter electrode flow into the substrate surface,
It is a kind of bias sputtering device.

On the other hand, US Pat. No. 3,325,394 describes a sputtering film forming technique using a cusp magnetic field. That is, the sputtering electrode and the film formation target substrate are arranged to face each other, and a cusp magnetic field is formed between the two sets of electromagnets to improve the plasma density and improve the film formation speed. In order to improve the deposition rate, the magnetron sputter deposition method, which has become publicly known after that, has a simpler device configuration and is more effective than the sputtering deposition method assisted by the cusp magnetic field. Its use was neglected.

[Problems to be solved by the invention]

Bias sputtering method deposits a film-forming material on a substrate and at the same time applies a negative bias voltage to the surface of the substrate to cause ions in the plasma to enter and apply the ion energy to the film-forming particles to move the surface of the film-forming particles. By increasing the degree,
It improves the throwing power to the grooves and holes. Therefore, it is important to improve the energy of the ions incident on the substrate. As a means for this, it is considered to improve the plasma density on the substrate to improve the ion current flowing into the substrate, or to improve the bias voltage. To be

Since the conventional magnetron sputter electrode confines plasma on the surface of the sputter electrode facing the substrate, simply applying a bias voltage to the substrate surface does not sufficiently improve the plasma density on the substrate. In our preliminary experiment, when the bias voltage was -100V, the plasma density on the substrate was about 2 × 10 ¹⁰ cm ^-3 , the ion current flowing into the substrate was about 0.5A / φ125, and 1.0μm square. Depth of
The adhesion of the film forming material (Al) to the 1.0 μm hole was not sufficient.

On the other hand, it is known that increasing the bias voltage increases the amount of Ar gas stored in the sputtered film. From our preliminary experiments, it was found that annealing after sputtering causes voids and swelling in the sputtered film formed at a high bias voltage, and the lower limit of this occurrence is about 140V.

An object of the present invention is to improve the ion current flowing into a substrate by a low bias voltage that does not cause film defects such as voids and swelling, and to adhere a film forming material well to fine steps, grooves or holes, in order to improve the ion current flowing into the substrate. To provide a method.

Another object of the present invention is to provide a sputtering method in which the ion energy incident on the substrate can be controlled by controlling the bias voltage while keeping the amount of ions flowing into the substrate substantially constant.

[Means for solving problems]

The above object is achieved by combining the high density of plasma using a cusp magnetic field and bias sputtering for applying a bias to the substrate-side electrode.

[Action]

By disposing the sputter electrode and the substrate electrode so as to face each other and forming a cusp magnetic field between them, high-density plasma is generated from the sputter electrode surface to the vicinity of the substrate surface. Furthermore, by applying a negative bias voltage to the substrate surface, high density ions in the plasma near the substrate surface are attracted to the substrate at a low bias voltage that does not cause film defects, and the substrate inflow ion current is improved. As a result, the mobility of the sputtered particles adhering to the substrate surface on the substrate surface is improved, or
The film material adhered to the corners of the upper part of the step, the groove, and the corners of the hole entrance on the substrate surface is sputtered and redeposited to the lower part of the step, the groove, and the bottom surface of the hole. Therefore, it is possible to improve the spread of the sputtered material on the step, the groove, and the hole without causing a film defect.

Since the bias voltage can be set independently of the generation of high-density plasma, the ion energy incident on the substrate can be controlled while keeping the ion current flowing into the substrate substantially constant.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First, the configuration of this embodiment will be described.

A sputter electrode 4 is attached to the opening 2 at the top of the vacuum container 1 via an insulator 3. A target 5 made of a sputtering film forming material is provided on the vacuum chamber side of the sputtering electrode 4, and a target coil 6 and a yoke 7 for generating a magnetic field are provided on the atmosphere side.
However, an anode 28 is attached to the vacuum container 1 via an insulator 8 on the outer periphery of the target 5 at a distance from the target that does not cause discharge to the target.

The yoke 7 is used to enhance the leakage magnetic flux density generated by the target coil 6.

The potential of the anode 28 is wired so as to be floating, ground, or any positive or negative potential, if necessary.

A substrate electrode 10 on which a substrate 25 is placed is provided in an opening 9 at the bottom of the vacuum container 1, and the surfaces of the target 5 and the substrate electrode 10 are surrounded by an insulator 11 having a vacuum sealing function. A substrate retainer 12 movable in a direction perpendicular to the substrate retainer 12 and a shield 14 around the substrate retainer 12 are fixedly attached to the vacuum container 1 via an insulator 13 having a vacuum sealing function. A substrate coil 17 is attached to another opening 15 at the bottom of the vacuum container 1 in a coil container 16 which is attached to the vacuum container 1 in a vacuum-sealed state.

The inside of the vacuum container 1 is evacuated by the evacuation means 18 and the gas is introduced by the gas introduction means 19, and mainly 10
^-3 Torr Pressure is maintained.

A sputtering power source 20, a high frequency power source 21, a DC power source 22, a target coil power source 23, a substrate coil power source 24, and a vacuum container 1 are attached to the sputtering electrode 4, the substrate electrode 10, the substrate retainer 12, the target coil 6, and the substrate coil 17, respectively. It is connected to earth.

The high frequency power supply 21 is not required when applying a DC bias voltage to the substrate surface, and the DC power supply 22 is not required when applying a high frequency bias voltage. When a high frequency bias voltage is applied, the substrate retainer 12 is made of an insulating material to shield high frequency plasma.

The target coil 6 and the target coil power supply 23 and the substrate coil 17 and the substrate coil power supply 24 are not limited to these electromagnets, and permanent magnets that generate a magnetic field equivalent thereto may be used.

The substrate 25 to be subjected to the sputtering film formation process is held on the substrate retainer 12 after being placed on the substrate electrode 10 by the transport mechanism (not shown) with the substrate retainer 12 being separated from the substrate electrode 10 on the target 5 side. It

The present embodiment having the above configuration operates as follows.

The substrate 25 transferred from the inlet (not shown) of the vacuum container 1 is
After being placed on the substrate electrode 10, it is fixed by the substrate retainer 12. After the inside of the vacuum container 1 is evacuated to a high vacuum by the evacuation means 18, Ar gas is introduced by the gas introduction means 19 to maintain a predetermined sputtering pressure. When a coil current is applied to the target coil 6 and the substrate coil 17 by the target coil power source 23 and the substrate coil power source 24 so as to generate mutually opposite magnetic fields, a cusp magnetic field having the shape of the magnetic force line 26 shown in FIG. 1 is generated. Occur. Further, when a sputtering voltage is applied to the sputtering electrode 4 from the sputtering power source 20, a high density plasma 27 having the same shape as the magnetic force lines 26 is generated from the surface of the target 5 to the vicinity of the surface of the substrate 25. A direct current bias is applied from the direct current power source 22 to the surface of the substrate 25 through the substrate retainer 12, or a high frequency power is applied to the substrate power source 10 from the high frequency power source 21 to further generate high frequency plasma on the substrate 25. By inducing a bias voltage on the surface, the substrate surface is kept at a negative bias potential, and the ions in plasma 27 are transferred to the substrate 25.
Is flowed over.

As described above, in this embodiment, since the high-density plasma can be generated up to the vicinity of the substrate 25 by the cusp magnetic field,
Even at a low bias voltage that does not cause a film defect, a step,
It is possible to obtain a sufficient ionic current for depositing a sputtering material on the grooves and holes and forming a film well.

An example of measurement of the inflow current in this embodiment is shown in FIG. FIG. 2 shows data when the substrate bias voltage is −100 V and the distance between the substrate and the target is 50 mm. When the ratio of substrate coil current / target coil current is small, the center diameter of the plasma ring is larger than the diameter of the substrate. By increasing this ratio, the center diameter of the plasma ring can be made equal to the diameter of the substrate. And a plasma density of 1 × 10 ¹¹ cm ^-3 , which is about 5 times that of the prior art,
About twice as much as 1.1A substrate inflow current (within φ125) was obtained.

Table 1 shows the results of determining the throwing power of Al from the SEM photograph when Al was deposited on the fine holes by the bias sputtering method while changing the ion current flowing into the substrate (hole depth: approx. 1 μm, film formation The speed is 1200 mm / min). The mark ○ indicates that Al adhesion to the side surface of the hole is approximately 40% or more of the film thickness of the flat portion. As described above, it was confirmed that when the ion current was 1 A / φ125, the Al coverage with the 1.0 square μm hole was sufficient.

Further, FIG. 3 shows the relationship between the bias voltage and the inflow current in this embodiment (the vertical axis is a relative unit). As in FIG. 2, the distance between the substrate and the target is 50 mm. Bias voltage
The inflowing ionic current is almost constant even if the voltage is changed from 100V to -40V. That is, it is possible to widely control the total ion energy incident on the substrate while keeping the ion current flowing into the substrate substantially constant.

〔The invention's effect〕

According to the present invention, it is possible to obtain a high substrate inflowing ion current with a low bias voltage, and therefore it is possible to adhere a sputtered film around steps, grooves, and holes without causing film defects such as voids and blisters. Also, because the substrate bias voltage can be set independently of the generation of high-density plasma,
The ion energy can be controlled while the amount of ions flowing into the substrate is kept substantially constant, and the margin of film quality control is improved.

[Brief description of drawings]

1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a diagram showing substrate inflow current data in the embodiment of the present invention, and FIG. 3 is a bias voltage and inflow current in the embodiment of the present invention. It is a figure which shows data. 1 ... vacuum container, 2 ... opening, 3 ... insulator, 4 ... sputtering electrode, 5 ... target, 6 ... target coil, 7 ... yoke, 8 ... insulator, 9 ... opening, Ten……
Substrate electrode, 11 ... Insulator, 12 ... Substrate retainer, 13 ... Insulator, 14 ... Shield, 15 ... Opening, 16 ... Coil container,
17 ... Substrate coil, 18 ... Exhaust means, 19 ... Gas introduction means, 20 ... Sputtering power source, 21 ... High frequency power source, 22 ... DC power source, 23 ... Target coil power source, 24 ... Substrate coil power source , 25 …… substrate, 26 …… magnetic field lines, 27 …… plasma,
28 …… Anode.

Claims (2)

[Claims] 1. A high-density plasma is generated by forming a cusp magnetic field between a target placed on a sputter electrode to which a voltage is applied and a sample substrate facing the target with a predetermined gap. Then, in the sputtering method adapted to sputter on the sample substrate, a negative bias voltage smaller than −140 V is applied to the substrate surface, and while the ions are incident on the substrate surface, the sputtering material ejected from the target is applied to the substrate. A sputtering method characterized by depositing and forming a film. 2. The sputtering method according to claim 1, wherein the bias voltage is −100V to −40V.