JP2502948B2 - Plasma deposition method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deposition method for forming thin films of various materials on a sample substrate in the production of electronic devices such as semiconductor integrated circuits, and more particularly to metal or metal utilizing plasma. The present invention relates to a plasma deposition method for forming a high quality thin film of a compound.

[0002]

2. Description of the Related Art Conventionally, SiO ₂ and S using plasma are used.
In forming a silicon-based thin film such as i ₃ N ₄ , a raw material is supplied in the form of a gas such as SiH ₄ , O ₂ and N _2, and plasma CVD (Chemical Vapor D) using high frequency discharge plasma is used.
eposition) method. However, this method has problems that it is necessary to heat the sample substrate to 250 to 400 ° C. and that the formed film is insufficient in terms of denseness. On the other hand, the CVD type ECR (El is designed to generate plasma under the electron cyclotron resonance condition using microwaves, draw the plasma onto the sample stage using the divergent magnetic field, and apply ion bombardment with appropriate energy.
In the ectron Cyclotron Resonance) plasma deposition method (see Japanese Patent Application No. 55-57877), it is possible to form a dense and high-quality silicon-based thin film comparable to the high temperature CVD method at a low temperature without heating the sample substrate. On the other hand, the sputtering method is generally widely used for metal and metal compound films. The sputtering method has an advantage that metal atoms can be easily supplied by sputtering a solid target.

Therefore, a sputter-type ECR plasma deposition method was developed by making use of the characteristics of both the CVD-type ECR plasma deposition method and the sputtering method (see Japanese Patent Application No. 57-156843), and the sample substrate is of high quality at low temperature without heating. It has become possible to form metal films and metal compound films. Furthermore, by changing the shape of the target from a conical cylinder shape to a right cylinder shape so that part of the plasma flow crosses the sputtering surface of the target, it is possible to greatly increase the target current and improve the film formation speed and film formation characteristics. (Japanese Patent Application Sho 58-1
55097).

The outline of the structure of the above-mentioned Japanese Patent Application No. 58-155097 and the principle of film formation will be described with reference to the sectional view shown in FIG. In FIG. 10, 1 is a plasma generation chamber, 2 is a sample chamber, 3 is a microwave introduction window, 4 is a rectangular waveguide, 5 is a plasma flow, 6 is a plasma extraction window, 7 is a sample substrate, 8 is a sample stage, 9 is an exhaust system, 10 is a magnetic coil, 11 is a magnetic shield, 12 is a first gas introduction system, 13 is a second gas introduction system,
14A and 14B are a cooling water supply port and a cooling water drain port, respectively.
Is a target electrode for sputtering, 16 is a shield electrode, 17 is a cooling tube, and 18 is a sputtering power source. For the plasma, after the plasma generation chamber 1 and the sample chamber 2 have been evacuated to a high vacuum by the exhaust system 9, a gas is introduced from one or both of the first gas introduction system 12 and the second gas introduction system 10 ⁻³ to 1
A pressure of about 0 ⁻¹ Pa is applied, and a plasma is generated by a microwave introduced from a microwave source (not shown) through the rectangular waveguide 4 and the microwave introduction window 3 sequentially and a magnetic field formed by the magnetic coil 10. It is formed in the generation chamber 1 using electron cyclotron resonance. Then, the ECR plasma thus formed and the particles sputtered from the target electrode 15 are transported to the sample stage 8 as a plasma stream 5.

The microwave source has a frequency of 2.45 GHz.
The electron cyclotron resonance condition at this time is a magnetic flux density of 875 G, and at least a part of the plasma generation chamber 1 satisfies this condition. In order to increase the electric field strength of microwaves and increase the discharge efficiency, the plasma generation chamber 1 is configured to satisfy the conditions of the microwave cavity resonator. For example, a TE ₁₁₂ mode cavity resonator is adopted, and the inner dimension is 15 cm in diameter. Height 15c
m cylindrical shape, and supply of cooling water, drain port 14
It is cooled using A and 14B. Plasma generation chamber 1
Then, circular motion electrons in a high energy state are formed by electron cyclotron resonance, and ECR plasma gas is formed by collision ionization with gas molecules. However, since the electrons have a magnetic moment due to circular motion, the magnetic coil 10
Due to the interaction with the divergent magnetic field in the direction of the sample stage, the plasma drawing window 6 accelerates while circularly moving and is guided toward the sample stage 8. Furthermore, since the sample stage 8 is electrically insulated from the plasma generation chamber 1, an electric field that decelerates electrons and accelerates ions is generated between the plasma generation chamber 1 and the sample stage 8, and the plasma is plasma. The plasma flow 5 is drawn out from the drawing window 6 toward the sample stage.
Due to the effect of this electric field, ions in the plasma flow are given appropriate ion energy for film formation.

The target electrode 15 has a right cylindrical shape in the vicinity of the plasma drawing window 6 of the sample chamber 2 in order to efficiently use highly active ECR plasma for sputtering.
It is placed at a position that crosses the plasma flow 5 and has a sputtering power source 1
8 and a negative voltage is applied. Then, in order to prevent abnormal discharge and incidence of unnecessary ions, the target electrode 15 is covered with a shield electrode 16 having a ground potential with a gap of 5 to 10 mm at a portion not facing the plasma flow 5. Also, supply of cooling water, drain port 14
By circulating cooling water through A and 14B and cooling the shield electrode 16 with water by the cooling pipe 17, the target electrode 15 is cooled by radiation heat conduction, and the temperature of the sample substrate 7 and the sample chamber 2 due to the heat of the target electrode. It has a structure that prevents it from rising.

In the above structure, for example, when argon (Ar) gas is introduced from the first gas introduction system 12 to generate plasma, the plasma flow 5 causes the target electrode 1 to flow.
The argon ions transported to the vicinity of the surface of No. 5 are accelerated by the negative voltage applied to the target electrode 15 and impinge upon the surface of the target electrode to give an impact, whereby atoms constituting the target electrode 15 are sputtered and the plasma flow 5 Jump out inside. The atoms are ionized in the plasma flow 5, are carried toward the sample stage 8 by the ion acceleration electric field generated in the plasma flow described above, are given appropriate ion energy, and enter the sample substrate 7. Adhesion
Deposit to form a good quality film at low temperature. The ion energy at this time is about 5 to 30 eV and can be controlled by microwave power, gas pressure, etc., so that the film quality can be freely controlled for thin films of a wide range of materials.

[0008]

As described above, according to the Japanese Patent Application No. 58-155097, the sputter type ECR is used.
By using the plasma deposition method and by arranging the target shape into a right cylinder shape so that part of the plasma flow crosses the sputtering surface of the target, the target current is greatly increased, and the film formation speed and film formation characteristics are improved. However, it is required to increase the ionization rate / activity of the adhered particles in order to efficiently transport the adhered particles and promote the film forming reaction by the plasma flow and further improve the film forming characteristics. It In particular, sputtered metal atoms have been conventionally ionized and activated by a structure in which a plasma flow passes through a straight cylindrical target electrode, but in addition to this, magnetron discharge on the target surface is used. By doing so, ionization and activation of metal atoms are further promoted, and the film formation characteristics can be controlled in a wider range by parameters such as gas pressure and sputtering voltage, contributing to dramatic improvement of characteristics and development of various thin film materials. It is expected that it will be possible.

[0009]

The present invention has been made in view of the above circumstances, and an object thereof is to further increase a target current by using a magnetron discharge in addition to an ECR discharge to increase the deposition rate. With the increase of
It is an object of the present invention to provide a plasma deposition method capable of improving the ionization and activation of sputtered metal particles and forming a good quality metal film or metal compound film at low temperature with good controllability.

The features of the present invention are: a sample chamber including a sample stage in which a sample substrate to be formed with a film to achieve the above object is arranged; a plasma generation chamber for introducing a gas to generate plasma; A plasma extraction window for guiding the generated plasma to the sample chamber as a plasma flow, and a target electrode arranged between the plasma extraction window and the sample stage, and a thin film on the sample substrate by sputtering the target electrode. In the plasma deposition method of depositing and depositing, the target electrode is an electrode that generates a local magnetic field such that a part of the magnetic field lines of the divergent magnetic field generated by the magnetic coil exits from one part of the sputter surface and returns to another part. The target material of the target electrode is made of metal, and the current value flowing through the target electrode in the voltage range of 100 V or more is steep. Applying a voltage exceeding the voltage raising,
The oxide film is characterized in that the oxygen partial pressure is set to about 1 to 3 × 10 ^-2 Pa.

That is, in the present invention, the structure of the target electrode 15 is modified so that a part of the divergent magnetic field generated by the magnetic coil 11 is in the vicinity of the sputtering surface of the target electrode 15 and the magnetic lines of force are on the sputtering surface. The electrode structure is such that a local magnetic field B is generated so that the local magnetic field B returns to another part from the above, and by this, an electromagnetic field represented by the relationship of E × B is realized between the sputtering field and the sputtering electric field E on the sputtering surface. This is intended to enable magnetron discharge near the surface. With this magnetron discharge, the target current is increased to dramatically improve the deposition rate, and the ionization and activation of the metal particles sputtered from the sputter surface are promoted. It is intended to further increase the film quality improving effect.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of an apparatus of the embodiment, FIG. 2 is an enlarged cross-sectional view of a target portion when a soft iron ring is used to generate a local magnetic field, FIG. It is a figure which shows the experimental result about the discharge characteristic and film formation characteristic which were each obtained by the said target structure.

In the embodiment of FIG. 1, the difference from the conventional structure of FIG. 10 lies in the structure of the target electrode 15, and the parts other than the target electrode 15 have the same structure and function. FIG. 2 is an enlarged view of the portion of the target electrode 15. FIG. 2 shows an embodiment in which a soft iron ring is used to generate a local magnetic field. The target electrode 15 has an inner diameter of 80 mm, a thickness of 2 mm, and a cylindrical target material 15A having a length of 55 mm in the cylinder axis direction, an inner diameter of 84 mm, and a thickness of 5 mm. , Axial length 24
mm soft iron ring 15B, inner diameter 84 mm, thickness 5 mm,
It is composed of a metallic support ring 15C having an axial length of 31 mm, and the cylindrical target material 15A is connected to a sputtering power source 18. The shield electrodes 16A, 16B, and 16C are kept at the ground potential, and prevent abnormal discharge of the target electrode and incidence of unnecessary ions on the target electrode. An insulating spacer 19 electrically insulates the target electrode and the shield electrode. 20 is an electrode pin, 21 is an insulating tube, 22 is a target support screw, and 23 is a target fixing screw.

With the construction of this embodiment, the soft iron ring 15B is formed.
Is magnetized by a divergent magnetic field generated by the magnetic coil 10 to easily generate a local magnetic field on the surface of the target material 15A. FIG. 3 shows the magnetic field line distribution estimated by measuring the magnetic field on the surface of the target material 15A. 24 is a magnetic field line in the vicinity of the target surface, 25 is a magnetic field vector (B), 26 is an electron transported by the plasma flow from the plasma generation chamber, 2
7 is an electron trapped in the magnetron discharge region, 28
Is a sputtering electric field (E), and 29 is a magnetron discharge region. The magnetic force lines 24 have a distribution in which the upper and lower portions of the target material 15A approach the surface of the target material, and the central portion of the magnetic field lines 24 moves away from the surface of the target material.
~ 300G. Then, this local magnetic field region exists up to about 10 mm from the surface of the target material 15A. The electrons obtain kinetic energy of E × B from the sputtering electric field 28 orthogonal to the magnetic field vector 25 and move while rotating along the lines of magnetic force. Thus, the electrons 26 transported by the plasma flow from the plasma generation chamber
And secondary electrons generated by sputtering are the target material 1
5A is confined near the surface due to the effect of the electromagnetic field,
A high density plasma region having a thickness of about 10 mm is formed on the surface of the target material 15A and becomes a magnetron region 29.

FIG. 4 shows the voltage-current characteristics of the target as an example of the characteristics of this embodiment. Ar gas was introduced from the first gas introduction system, O ₂ gas was introduced from the second gas introduction system, Al was used as the target material, and the microwave power was 300 W.
That is the case. At an Ar gas flow rate of 10 SCCM and an O ₂ gas flow rate of 5 SCCM (1.8 × 10 ⁻¹ Pa), in the case of the present embodiment, a target voltage of about 300 V is obtained when compared with the case where only the right cylindrical target shown in FIG. 10 is used. The target current greatly increases in response to the generation of the magnetron discharge, and reaches 1.5 times the target voltage of 500V. This tendency becomes remarkable as the gas pressure increases, and
It can be seen that when the gas flow rate is 20 SCCM and the O ₂ gas flow rate is 10 SCCM, the target current rapidly increases at the target voltage of 300 V, and the magnetron discharge is stably generated on the surface of the target material.

FIG. 5 shows the film forming characteristics of Al ₂ O ₃ ,
The case of using the configuration of the present embodiment and the configuration using the conventional right cylindrical target will be compared and shown. The Ar gas flow rate was 18 SCCM and the target voltage was 400 V. In the conventional configuration, the microwave power was increased to match the target current with the configuration of this example using the soft iron ring. With respect to the refractive index, when the O ₂ gas flow rate is ₂ SCCM or more, both target configurations show about 1.6, which is a value peculiar to the Al ₂ O ₃ film. However, in the case of the configuration of this example, the deposition rate is significantly improved in the low oxygen partial pressure region, and the deposition efficiency is increased.

As described above, by forming a local magnetic field in the vicinity of the target with the target electrode structure shown in the embodiment of FIG. 2, in addition to ECR discharge, a high density plasma region in the magnetron discharge mode is generated in the vicinity of the target surface. Stable formation at a low gas pressure, resulting in a large increase in target current and an increase in the ionization rate of adhered particles centered on sputtered particles, enabling plasma flow transport to increase the deposition rate at an accelerated rate. Becomes Also,
According to the present embodiment, only by arranging the soft iron ring 15B on the back surface of the target material 15A, it is possible to form a local magnetic field on the target surface without affecting the divergent magnetic field in the portion away from the target.

6 and 7 show another embodiment of the present invention, respectively.
The formation structure of a local magnetic field is shown. In FIG. 6, ring-shaped magnets 15D that are magnetized in the radial direction into N-poles and S-poles are arranged above and below the back surface of the cylindrical target material 15A with a metal ring 15C interposed therebetween. As the material of the ring-shaped magnet 15D, Alnico 5 or the like is used in consideration of the high temperature of the target surface and the conductivity. FIG. 7 shows the target material 1.
The back surface of 5A has a metal support ring 15C on its entire surface,
The local magnetic field generating coil 30 is wound around the outside. According to the target configurations of FIGS. 6 and 7, since the magnetic force lines that cross the target increase, it becomes possible to suppress the dissipation of electrons from the high-density plasma region formed on the surface of the target material, and it is possible to suppress the secondary electrons. Even when Ta or the like having low generation efficiency is used as the target material, there is an advantage that a stable magnetron discharge mode can be obtained.

FIGS. 8 and 9 are cross-sectional views showing still another embodiment of the present invention, showing a target structure in which the efficiency and the gas pressure of the magnetron discharge mode are reduced. Generally, in the lower part of the target electrode, electrons in the high-density plasma formed on the target surface flow into the shield electrode which is kept at the ground potential, and the sputtering electrode disturbs the sputtering electric field. It is easy to dissipate to the outside. In the configuration of the embodiment of FIG. 8, in order to improve the above two points, the lower shield electrode 16C is arranged via the quartz plate 16D, and the target flange 31 is added to the lower surface of the target material 15A. According to the embodiment of FIG. 8, although the target structure is slightly complicated, electrons can be pushed back to the high density plasma region of the target surface, and the voltage-current characteristics similar to those of FIG. 4 are stable at a lower gas pressure. There are advantages to be obtained.

Further, FIG. 9 shows that electrons in the lower part of the target electrode are prevented from being dissipated outside the high-density plasma region,
Another embodiment for stabilizing the magnetron discharge mode is shown. In this target configuration, similarly to the embodiment shown in FIG. 8, a quartz plate 16D is arranged, and a soft iron ring having a length of about ½ of the soft iron ring arranged above the target electrode 15A is also used as the target material 15A. Place it on the back side of. With this configuration, most of the magnetic force lines associated with the local magnetic field end in the lower part of the target, and it is possible to efficiently confine the electrons moving along the magnetic force lines into the high-density plasma region on the target surface. In fact, with this target structure, good characteristics were obtained at a target voltage of 500 V at a low gas pressure, a target current of 2 A, and a film formation rate of about 1000 Å / min for an Al ₂ O ₃ film. The film obtained at this time had a refractive index of 1.65 and had an Al ₂ O ₃ content of
The same value as the bulk value of the film was obtained, and an Al ₂ O ₃ film in which the oxidation reaction was sufficiently advanced even in the high-speed deposition was obtained.

[0021]

As described above, according to the present invention,
In the sputtering type ECR plasma deposition device, by supplying electrons by ECR discharge, magnetron discharge at low gas pressure near the surface of the target material is possible, thereby increasing target current at low gas pressure and improving deposition rate. It will be possible. In addition, this magnetron discharge accelerates the ionization and activation of sputtered metal particles, further enhances the transport effect of adhered particles by the plasma flow and the film quality improvement effect by ion bombardment, resulting in high-quality metal films and metal compound films. Can be formed with high adhesion efficiency and further improved controllability of film quality and the like. Particularly for the metal compound film, since the reactive gas is also activated by the magnetron discharge, the chemical reaction law is relaxed and the deposition rate and the film quality can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part in FIG.

FIG. 3 is a magnetic field line measurement diagram with the target configuration of FIG. 2.

FIG. 4 is a diagram showing discharge characteristics obtained with the target configuration of FIG.

5 is a diagram showing an experimental result of film forming characteristics obtained by the target configuration of FIG.

FIG. 6 is a cross-sectional view of essential parts showing another embodiment of the present invention.

FIG. 7 is a cross-sectional view of essential parts showing another embodiment of the present invention.

FIG. 8 is a sectional view of a target portion showing still another embodiment of the present invention.

FIG. 9 is a sectional view of a target portion showing still another embodiment of the present invention.

FIG. 10 is a sectional view showing a conventional configuration.

[Explanation of symbols]

 1 ... Plasma generation chamber 2 ... Sample chamber 3 ... Microwave introduction window 4 ... Rectangular waveguide 5 ... Plasma flow 6 ... Plasma extraction window 7 ... Sample substrate 8 ... ..Sample stage 9 ... Exhaust system 10 ... Magnetic coil 11 ... Magnetic shield 12, 13 ... Gas introduction system 14 ... Cooling water supply / drainage port 15 ... Target electrode 15A ..Cylindrical target material 15B ... Soft iron ring 15C ... Metal support ring 15D ... Ring magnets 16A, B, C ... Shield electrode 16D ... Quartz plate 17 ... Cooling tube 18・ ・ ・ Sputtering power source 19 ・ ・ ・ Insulating spacer 24 ・ ・ ・ Magnetic field line 25 ・ ・ ・ Magnetic field vector 28 ・ ・ ・ Sputtering electric field 29 ・ ・ ・ Magnetron discharge area 30 ・ ・ ・ Local magnetic field generating coil 31 ・ ・ ・ Target brim

Claims (1)

(57) [Claims] 1. A sample chamber including a sample stage on which a sample substrate to be formed with a film is arranged, and a gas is introduced to generate a plasma by an electron cyclotron resonance discharge by a magnetic field formed by a magnetic coil and a microwave. The plasma generation chamber and the magnetic coil are magnetic field sources that generate a divergent magnetic field in which the magnetic field strength is gradually weakened from the plasma generation chamber toward the sample stage in order to draw plasma from the plasma generation chamber to the sample stage, It has a plasma extraction window for guiding the generated plasma to the sample chamber and a target electrode arranged between the plasma extraction window and the sample stage, and a thin film is deposited on the sample substrate by sputtering the target electrode. In the plasma deposition method of depositing, the divergent magnetic field generated by the magnetic coil is applied to the target electrode. An electrode for generating a local magnetic field in which a magnetic field of a part of the magnetic field is emitted from a certain portion of the sputtering surface and returned to another portion, the target material of the target electrode is made of metal, and the target electrode in a voltage range of 100 V or more is used. A plasma deposition method, characterized in that a voltage exceeding the voltage at which the current flowing through the electrode rapidly increases is applied to form an oxide film with an oxygen partial pressure of about 1 to 3 × 10 ^-2 Pa.