JPH0691013B2 - Plasma deposition device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adhesion device 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 plasma deposition devices. The present invention relates to a plasma deposition apparatus for forming a thin film of a metal or a metal compound with high quality at low temperature.

[Conventional technology]

Conventionally, in the formation of silicon-based thin films such as SiO ₂ and Si ₃ N ₄ using plasma, the raw material is supplied in the form of gas such as SiH ₄ , O ₂ and N _2, and plasma CVD (C
hemical vapor deposition) 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, a CVD type ECR (El is designed to generate plasma under the conditions of electron cyclotron resonance using microwaves, draw plasma on the sample stage using a divergent magnetic field, and apply ion bombardment with appropriate energy.
ectron Cyclotron Resonance) Plasma deposition method
55-57877), it is possible to form a dense and high-quality silicon-based thin film comparable to the high temperature CVD method at 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 a high-quality metal film at a low temperature that does not heat the sample substrate was formed. It became possible to form a metal compound film. Furthermore, by changing the shape of the target from a conical cylinder shape to a right cylinder shape and arranging a part of the plasma flow so as to cross the sputtering surface of the target, the target current can be greatly increased and the film formation speed and film formation characteristics can be improved. (See Japanese Patent Application No. 58-155097).

The outline of the construction 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. 9, 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 cooling water supply and drain ports respectively, and 15 is for sputtering Target electrode, 16 is a shield electrode, 17 is a cooling tube, 1
8 is a sputtering power source. For the plasma, after the plasma generation chamber 1 and the sample chamber 2 are 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 to a pressure of about 10 ^-3 to 10 ^-1 Pa, and a rectangular waveguide 4 and a microwave are supplied from a microwave source (not shown). The microwaves sequentially introduced through the introduction window 3 and the magnetic coil 10
It is formed by using electron cyclotron resonance in the plasma generation chamber 1 by the magnetic field formed by 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.

A magnetron with a frequency of 2.45 GHz can be used as the microwave source, and 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 the microwave and 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. It has a cylindrical shape with a height of 15 cm, and is cooled by using cooling water supply and drainage ports 14A and 14B. In the plasma generation chamber 1, high-energy circular motion electrons are formed by electron cyclotron resonance, and ECR plasma gas is formed by impact ionization with gas molecules. Since the electrons have a magnetic moment due to circular motion, By the interaction with the divergent magnetic field in the direction of the sample stage generated by the magnetic coil 10, the plasma is drawn out toward the sample stage 8 while being circularly accelerated from the plasma drawing window 6. Furthermore, the sample table 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 plasma is generated from the plasma extraction window 6 through the plasma extraction window 6. A stream 5 is drawn 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.

In order to efficiently use highly active ECR plasma for sputtering, the target electrode 15 has a right cylindrical shape, which is arranged in the vicinity of the plasma extraction window 6 of the sample chamber 2 and at a position where the plasma flow 5 is crossed. It is connected to 18 and a negative voltage is applied. And the target electrode 15 is
In order to prevent abnormal discharge and incidence of unnecessary ions, a portion not facing the plasma flow 5 is covered with a shield electrode 16 having a ground potential with a gap of 5 to 10 mm. Further, by circulating the cooling water through the cooling water supply / drainage ports 14A and 14B and cooling the shield electrode 16 with water by the cooling pipe 17, the target electrode 15 is cooled by radiative heat conduction, and the sample by the heat of the target electrode is cooled. The structure is such that the temperature inside the substrate 7 and the sample chamber 2 is prevented from rising.

In the above configuration, for example, when plasma is generated by introducing argon (Ar) gas from the first gas introduction system 12,
The argon ions transported to the vicinity of the surface of the target power supply 15 by the plasma flow 5 are accelerated by the negative voltage applied to the target electrode 15 and are incident on the surface of the target electrode to give an impact to the atoms constituting the target electrode 15 It is sputtered and jumps out into the plasma stream 5. 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, and are given appropriate ion energy to enter the sample substrate 7, It adheres and deposits to form a good quality film at low temperature. The ion energy at this time is about 5 to 30 eV, and it can be controlled by microwave power or gas pressure, so that the film quality can be freely controlled for a wide range of thin films.

As described above, according to Japanese Patent Application No. 58-155097, the sputter type ECR plasma deposition method is used, and the target shape is made into a right cylindrical shape so that a part of the plasma flow crosses the sputter surface of the target. As a result, the target current was greatly increased and the film formation speed and film formation characteristics were improved. However, the plasma flow facilitated the efficient transport of adhered particles and the promotion of the film formation reaction. In order to further improve the
Increased activity is desired. In particular, sputtered metal atoms have been conventionally ionized and activated by a structure in which a plasma flow passes through a right-cylindrical target electrode. In addition to this, magnetron discharge or the like on the target surface is performed. If it is used, the ionization and activation of metal atoms can be calculated more rapidly, and the film formation characteristics can be controlled in a wider range by the parameters of gas pressure and sputtering voltage, which contributes to the dramatic improvement of characteristics and the development of various thin film materials. It is expected that it will be possible.

[Object of the Invention]

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

[Outline of Invention]

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;
It has 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 is formed on the sample substrate by sputtering the target electrode. In the plasma deposition apparatus for depositing / depositing a target electrode, the target electrode has an electrode structure for forming a local magnetic field in the vicinity of the sputtering surface, magnetic force lines formed by the local magnetic field are substantially orthogonal to the sputtering electric field, and a part of the magnetic force line is on the target surface. It is to be a local magnetic field that exits from and returns to the target surface again.

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 near the sputtering surface of the target electrode 15.
An electrode structure that generates a local magnetic field so that the lines of magnetic force emerge from one part of the sputter surface and return to another part, and an electromagnetic field represented by the relationship x with the sputtering electric field on the sputter surface is realized. Then, it is intended to enable magnetron discharge in the vicinity of the sputtering 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, and the transport effect of the deposited particles by the plasma flow
It is intended to further increase the film quality improving effect by ion bombardment.

Example of Invention

An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of the embodiment apparatus, 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, and FIG. 3 is a magnetic field line estimation diagram in the above target configuration, FIG. , FIG. 5 is a diagram showing the experimental results on the discharge characteristics and the film formation characteristics obtained by the above target configuration, respectively.

In the embodiment shown in FIG. 1, the difference from the conventional structure shown in FIG. 9 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 length of 55 m in the axial direction of the cylinder.
It is composed of a cylindrical target material A15A of m, inner diameter 84mm, thickness 5mm, soft iron ring 15B with axial length 24mm, metal support ring 15C with inner diameter 84mm, thickness 5mm, axial length 31mm. The converted target material 15A is connected to the sputtering power source 18. 16A, 16B, 16C are kept at ground potential by shield electrodes,
Prevents abnormal discharge of the target electrode and unwanted ions from entering 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 configuration of this embodiment, the soft iron ring 15B has the magnetic coil 1
The local magnetic field is easily generated on the surface of the target material 15A by being magnetized by the divergent magnetic field created by 0. Figure 3, Target material 15
The magnetic field distribution is estimated by measuring the magnetic field on the surface of A. 24 is the magnetic field line near the target surface, 25 is the magnetic field vector (), 26 is the electrons transported by the plasma flow from the plasma generation chamber, 27 is the electrons trapped in the magnetron discharge region, 28 is the sputtering electric field (), 29 Is a magnetron discharge region. Magnetic field line 24 is target material 15A
The distribution approaches the surface of the target material at the top and bottom of the, and moves away from the surface of the target material at the center, and its size is 200-300G. Then, this local magnetic field region exists up to about 10 mm from the surface of the target material 15A. Electrons are generated from the sputtering electric field 28 which is orthogonal to the magnetic field vector 25 ×
The target material 15A is repelled due to the sputtering electric field at the upper and lower parts of the target material 15A. Thus, the electrons 26 transported by the plasma flow from the plasma generation chamber and the secondary electrons generated by the sputtering are trapped near the surface of the target material 15A by the effect of the electromagnetic field, and
A high-density plasma region having a thickness of about 10 mm is formed on the surface of 15A and becomes a magnetron region 29.

FIG. 4 shows the target voltage-current characteristics 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, and Al was used as the target material.
Is used and the microwave power is set to 300W. Ar
When the gas flow rate is 10 SCCM and the O ₂ gas flow rate is 5 SCCM (1.8 × 10 ⁻¹ Pa), the magnetron discharge at the target voltage of about 300 V is obtained in the present embodiment as compared with the case where only the right cylindrical target shown in FIG. 9 is used. The target current greatly increases in response to the occurrence of, and reaches 1.5 times the target voltage of 500V. This tendency becomes remarkable as the gas pressure increases, and the target voltage is 300 SC at an Ar gas flow rate of 20 SCCM and an O ₂ gas flow rate of 10 SCCM.
It can be seen that the target current rapidly increases at V, and the magnetron discharge is stably generated on the target material surface.

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

As described above, by forming a local magnetic field in the vicinity of the target in the target electrode configuration shown in FIG. 2, the high density plasma region in the magnetron discharge mode near the target surface has a low gas pressure in addition to the ECR discharge. Stable formation, and as a result, the target current is greatly increased, and the ionization rate of the adhered particles centering on the sputtered particles is improved, so that the plasma flow transport makes it possible to increase the deposition rate at an accelerated rate. Further, 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.

FIG. 6 shows a configuration of forming a local magnetic field according to another embodiment of the present invention. In FIG. 6, ring-shaped magnets 15D magnetized in N and S poles in the radial direction are arranged above and below the back surface of the cylindrical target material 15A with a metal ring 15C interposed therebetween. As a material for the ring-shaped magnet 15D, Alnico 5 or the like is used in consideration of the high temperature of the target surface and conductivity.
Fig. 6 shows that, according to the target configuration, the magnetic field lines that cross the target increase, so it becomes possible to suppress the dissipation of electrons from the high-density plasma region formed on the target material surface, and the secondary electron generation efficiency. The advantage is that a stable magnetron discharge mode can be obtained even when Ta, which has a low value, is used as the target material.

FIG. 7 and FIG. 8 are sectional views showing still another embodiment of the present invention, and show a target configuration in which the efficiency of magnetron discharge mode and the gas pressure 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 that 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. 7, in order to improve the above two points, the lower shield electrode 16C is arranged via the quartz plate 16D, and
The target collar 31 is added to the lower surface of the target material 15A. According to the embodiment of FIG. 7, 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 can be obtained at a lower gas pressure. There is an advantage that it can be obtained stably.

Further, FIG. 9 shows another embodiment for preventing the dissipation of electrons in the lower part of the target electrode to the outside of the high-density plasma region and stabilizing the magnetron discharge mode.
In this target structure, as in the embodiment shown in FIG. 7, a quartz plate 16D is arranged, and a soft iron ring having a length of about 1/2 of the soft iron ring arranged above the target electrode is also used as the target material. Place on the back of 15A. With this configuration, most of the magnetic force lines associated with the local magnetic field end at 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 configuration, we obtained good characteristics with a film formation rate of 1000Å / min for a target current of 2A and an Al ₂ O ₃ film at a target voltage of 500V at a low gas pressure. The film obtained at this time has a refractive index
In 1.65, Al ₂ O ₃ are the same value is obtained as the bulk values of the film, Al ₂ O ₃ film advanced a sufficient oxidation reaction even at high adhesion was obtained.

〔The invention's effect〕

As described above, according to the present invention, the sputter type ECR is used.
By supplying electrons to the plasma deposition device by ECR discharge to enable magnetron discharge at low gas pressure near the surface of the target material, it is possible to increase the target current and the deposition rate at low gas pressure. Also, this magnetron discharge causes ionization of sputtered metal particles.
Activation is promoted, the transport effect of adhered particles by the plasma flow and the film quality improvement effect by ion bombardment are further increased, and high quality metal films and metal compounds are formed with high adhesion efficiency and controllability of film quality and the like. it can. For metal compounds, in particular, the reactive gas is also activated by magnetron discharge, so the chemical reaction law is relaxed and the deposition rate and film quality can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is an enlarged view of a main part in FIG. 1, and FIG. 3 is a strong line measurement diagram in FIG. 2 target configuration, FIG. 4, FIG. The figures are the experimental results of the discharge characteristics and the film formation characteristics obtained by the above target structure, respectively. FIG. 6 is a sectional view of an essential part showing another embodiment of the present invention, and FIG. 7 and FIG. FIG. 9 is a sectional view of a target portion showing the embodiment of FIG. <Explanation of reference 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 stand 9 …… Exhaust system, 10 …… Magnetic coil 11 …… Magnetic shield, 12,13 …… Gas introduction system 14 …… Cooling water supply / drain port, 15 …… Target electrode 15A …… Cylinder Target material, 15B …… Soft iron ring 15C …… Metal support ring, 15D …… Ring magnet 16A, B, C …… Shield electrode, 16D …… Quartz plate 17 …… Cooling tube, 18 …… Sputtering power source 19 …… Insulating spacer, 24 …… Magnetic field 25 …… Magnetic field vector 28 …… Sputtering electric field 29 …… Magnetron discharge area 31 …… Target brim

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seitaro Matsuo 1839 Ono, Atsugi City, Kanagawa Pref. Atsugi Telecommunications Research Laboratories, Nippon Telegraph and Telephone Corporation (56) Reference JP-A-59-47728 (JP, A) JP A 52-44174 (JP, A)

Claims (2)

[Claims] 1. A sample chamber including a sample stage in 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 that guides the generated plasma to the sample chamber, and a target electrode that is arranged between the plasma extraction window and the sample stage, and deposits a thin film on the sample substrate by sputtering the target electrode. In the plasma deposition apparatus for depositing, a part of the magnetic field lines of the divergent magnetic field generated by the magnetic coil is spun. A local magnetic field that goes out from a certain portion of the surface of the magnet and returns to another portion, near the sputtering surface of the target electrode, having a soft iron ring generated by magnetizing by a divergent magnetic field created by the magnetic coil, A plasma deposition apparatus having an electrode structure in which a soft iron ring is closely and integrally arranged on the outer diameter side of a right cylindrical target material. 2. A sample chamber including a sample stage in 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 microwaves. 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 that guides the generated plasma to the sample chamber, and a target electrode that is arranged between the plasma extraction window and the sample stage, and deposits a thin film on the sample substrate by sputtering the target electrode. In the plasma deposition apparatus for depositing, the target electrode is placed near the sputtering surface of the target electrode. One of the divergent magnetic fields generated by the magnetic coil is a local magnetic field in which a magnetic field line of a part of the divergent magnetic field goes out from a certain part of the sputtering surface and returns to another part. The other one is generated by a ring-shaped permanent magnet that is magnetized in the radial direction to the N pole and the S pole and is arranged integrally in close contact with the outer diameter side of the right cylindrical target material. A plasma deposition device having a structure.