JP2832256B2 - Plasma deposition equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to plasma deposition for forming thin films of various materials on a sample substrate in the manufacture of electronic devices such as semiconductor integrated circuits and surface treatment of various materials. The present invention relates to an apparatus, and more particularly, to a plasma deposition apparatus for forming a thin film of a metal or a metal compound with high quality at a low temperature using plasma.

[Prior Art] Conventionally, as a thin film forming method using plasma, a plasma CVD method for supplying a raw material in a gas form has been widely used. However, this method has a problem that the sample substrate needs to be heated to 250 to 400 ° C., and the formed film is insufficient in the tightness. In contrast, a CVD type ECR (Electron Cyclotron Resonance) plasma deposition method using electron cyclotron resonance plasma by microwaves (Japanese Patent Application Laid-Open No. 56-155535) is comparable to high-temperature CVD at a low temperature without heating the sample substrate. A dense and high-quality thin film can be formed.

In contrast, for metal and metal compound films,
Generally, a sputtering method is widely used. The sputtering method has an advantage that a metal source can be easily supplied by sputtering a solid target. Therefore, a sputter type ECR utilizing the advantages of the CVD type ECR plasma deposition method and the sputtering method
The plasma deposition method (JP-A-59-47728) was developed,
Development of a straight cylindrical target (JP-A-60-50167),
The use of magnetron mode discharge (Japanese Patent Application Laid-Open No. 61-114518) has made it possible to greatly increase the target current and improve the film formation speed and film formation characteristics.

FIG. 4 shows an outline of the structure of the apparatus disclosed in Japanese Patent Application Laid-Open No. 61-114518 and the principle of film formation. In FIG. 4, 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, and 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, 14 is a cooling water pipe, 15 is a sputtering target, 16 is a soft iron for a local magnetic field. The ring, 16A is a ring made of a nonmagnetic conductor such as stainless steel, for example, 17 is a shield electrode, 17A is an insulator, 18 is a cooling water pipe, and 19 is a sputter power supply. 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 13 to a pressure of about 10 ^-3 to 10 ^-1 Pa, and a rectangular wave guide 4 and a microwave are supplied from a microwave source (not shown). The microwave introduced through the wave introduction window 3 and the magnetic coil 10
A plasma is generated in the plasma generation chamber 1 using electron cyclotron resonance by the magnetic field formed by The plasma is extracted from the plasma extraction window 6 in the direction of the sample stage and forms a plasma stream 5. In contact with the plasma stream 5,
In addition, since the target 15 is disposed so as to surround the target, a negative voltage is applied to the target 15 by the sputtering power supply 19 to perform sputtering by ions in the plasma flow 5.

As the microwave source, a magnetron having a frequency of 2.45 GHz can be used. The electron cyclotron resonance condition at this time is a magnetic flux density of 875 G, and this condition is satisfied in at least a part of the plasma generation chamber 1. Plasma generation chamber 1
Increases the electric field intensity of the microwaves in order to increase the efficiency of plasma generation, a structure of a microwave cavity resonator, for example, employ a resonant cavity of the TE ₁₁₂ mode, 15cm diameter at inner dimension, height 15cm It has a cylindrical shape and is cooled by a cooling water pipe 14 to prevent heating by plasma.
The magnetic field generated by the magnetic coil 10 gives the plasma generation chamber 1 a magnetic flux density under the electron cyclotron resonance condition, and forms a divergent magnetic field that weakens in the direction from the plasma generation chamber 1 to the sample stage 8. Further, a magnetic shield 11 is provided to prevent unnecessary spread of a magnetic field to the outside. In the plasma generation chamber 1, circularly moving electrons in a high energy state are formed by electron cyclotron resonance, and plasma is formed by impact ionization with gas molecules. Circular motion electrons are accelerated while moving circularly from the plasma extraction window 6 and guided toward the sample stage 8 due to the interaction between the magnetic moment of the electron and the divergent magnetic field generated by the magnetic coil 10. Since the sample stage 8 is electrically insulated from the plasma generation chamber 1, an electric field is generated between the plasma generation chamber 1 and the sample stage 8 to decelerate electrons and accelerate ions. From the sample stage toward the sample stage. Due to the effect of the electric field, ions in the plasma flow are given an appropriate ion energy for film formation.

The sputtering target 15 is formed in a straight cylindrical shape in the vicinity of the plasma extraction window 6 of the sample chamber 2 in contact with the plasma flow 5 and at a position surrounding the plasma flow window 5 in order to efficiently use the highly active ECR plasma for sputtering. Then, it is connected to a sputtering power supply 19 and a negative voltage is applied. In addition, the local magnetic field soft iron ring 16 forms a local magnetic field near the target surface where the magnetic field lines exit from the target and return to the target, and satisfy the ExB condition in which the electric field and the magnetic field are orthogonal to the sputtering region of the target 15. The magnetron mode high-density plasma is generated to improve the sputtering efficiency. Since the local magnetic field exists only near the target surface, a high-quality film can be formed at high speed while maintaining the effect of ion transport by the plasma flow 5. Further, the portion of the target 15 not facing the plasma flow 5 is covered with a shield electrode 17 of a ground potential with a gap of 5 to 10 mm in order to prevent abnormal discharge and incidence of unnecessary ions. Also, the target 15 prevents heating by sputtering,
It is cooled by a cooling water pipe 18.

[Problem to be Solved by the Invention] In the above configuration, for example, the first gas introduction system 12
Ar was introduced from the second gas introduction system 13 into O ₂ , and the target 1
When Al is used for 5, a high-quality alumina (Al ₂ O ₃ ) film is formed at a high speed of 1000 ° / min or more. This is due to the high-speed supply and activation of the metal raw material by magnetron mode sputtering, and the reaction promoting effect of moderate ion bombardment on the film formation by the plasma flow. However, if an attempt is made to obtain a higher deposition rate, the electric field of the target is spread in the plasma flow, abnormal discharge occurs, and it has been difficult to form a stable film. Furthermore, sputtering using only Ar gas has a disadvantage that a conductive aluminum (Al) film adheres to the microwave introduction window, making it difficult to introduce microwaves and making stable plasma generation difficult.

As described above, according to the apparatus disclosed in JP-A-61-114518, it is possible to improve the film formation speed and film formation characteristics in forming a dielectric film by the sputter type ECR plasma deposition method. However, it is desired to further stabilize the sputter discharge and improve the controllability of ion energy, and to realize the formation of a conductive film of a metal or a metal compound.

The present invention has been made in view of the above circumstances, and its object is to irradiate a plasma drawn from a plasma extraction window, a ring-shaped plasma flow for irradiating a sputtering target, and a sample substrate in a sputtering type plasma deposition method. To stabilize sputter discharge characteristics and film formation characteristics by ion flow irradiation by limiting the spread of the sputter electric field into the plasma flow irradiating the sample. In addition to the above, in addition to the above, a plasma deposition apparatus that can form various metal and metal compound thin films with high controllability and reliability by removing metal particles directly flying from a sputtering target to a microwave introduction window. Is to provide.

[Means for Solving the Problems] A plasma deposition apparatus according to the present invention includes a plasma generation chamber for introducing a gas to generate plasma, and a sample chamber in which a sample stage on which a sample substrate on which a film is to be formed is arranged. A plasma extraction window disposed between the plasma generation chamber and the sample chamber for introducing plasma from the plasma generation chamber into the sample chamber as a plasma flow; and a plasma surrounding the plasma flow formed of a sputtering material and surrounding the plasma flow. A target disposed in contact with the flow, ions for sputtering the target are extracted from a portion of the plasma flow and incident on the target,
In the plasma deposition apparatus for depositing and depositing a thin film on a sample substrate by sputtering the target, the plasma extraction window has an opening at the center and an outer periphery smaller than the inner periphery of the plasma generation chamber. It is characterized by having a structure in which the plasma flow is divided into a plasma flow guided to the sample stage and a plasma flow guided to the target by being fixed to the generation chamber.

[Operation] In the present invention, the plasma introduction window has a unique structure. Therefore, by separating the plasma applied to the sample substrate, a film can be stably formed with high reliability and controllability.

Examples Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of an apparatus according to an embodiment of the present invention, FIG. 2 is a schematic view showing the arrangement of a target, a plasma extraction window and a microwave introduction window in the present invention, and FIG. 3 is a schematic view of a target electric field distribution. .

In the embodiment shown in FIG. 1, the difference from the conventional structure shown in FIG. 4 lies in the structure of the plasma extraction window 6 and the arrangement position of the target 15 associated therewith. It is. FIG. 2 is an enlarged view of the vicinity of the plasma extraction window, and details of the embodiment of the present invention will be described with reference to FIG.

FIG. 2 shows the geometrical arrangement of the target 15, the plasma flow 5, the plasma extraction window 6, the microwave introduction window 3, and the sample stage 8. The plasma extraction window 6 includes a ring-shaped extraction window 6A and a circular extraction window 6B for irradiating the target with the ring-shaped plasma flow 5A and the column-shaped plasma flow 5B on the sample stage 8 separately therefrom. ing. In addition, a ring-shaped plasma cutoff section 6C between them
Thereby, the microwave introduction window 3 cannot be seen directly from the target. The plasma cutoff unit 6C has, for example, three or four radial support portions (not shown), and these radial support portions are fixed to an end of the plasma generation chamber by a known method such as bolting.

First, stabilization of the sputter discharge will be described with reference to FIG. When sputtering is performed by applying a negative potential to the target 15, most of the electric field is applied to the sheath portion near the target surface, and the rest is applied to the space with the surrounding ground plane via the plasma. This is schematically shown by the broken line (a) in FIG. In addition, when sputtering is performed at a high speed as in magnetron mode sputtering, and the secondary electrons generated for this purpose are not sufficiently captured by the target, or in the case of sputtering in which the secondary electrons are not captured by sputtering in principle. As shown by the solid line (b) in FIG. 3, a high electric field is applied to the space with the surrounding ground plane. On the other hand, according to Parsien's law, the voltage at which spark discharge occurs in the equal electric field gap (spark voltage) differs depending on the gas type, gas pressure, and gap interval. For example, the spark voltage at an Ar gas of 1 × 10 ⁻³ Torr and a gap interval of 100 cm is 200 V. It is known that a gap interval and a spark voltage at which a spark discharge occurs become extremely small when electrons or ions are already present or when plasma is present, so that a spark discharge is easily generated. It can be assumed that abnormal discharge in sputtering is triggered by spark discharge. The line (a) in FIG. 3,
In the case where the target electric field is applied between the target surface and the ground plane as in (b), if the distance and the voltage conform to Parsien's law, abnormal discharge is likely to occur. In the conventional configuration shown in FIG. 4, the voltage applied to the target extends over a wide range of the plasma generation chamber 1 and the sample stage 8 via the plasma, so that a distance that conforms to the Parcien's law is easily realized, and therefore, the abnormal Discharge is likely to occur. On the other hand, in the configuration of the present invention shown in FIG. 2, the ring-shaped extraction window 6A is made to have an appropriate size so that the ring-shaped plasma 5A is extracted from the plasma extraction window, and the target electric field soaked into the ring-shaped plasma. Can be limited to a distance equal to or less than the distance in Parsien's law, and stable sputtering without abnormal discharge can be realized. The distribution of the target electric field at this time is shown by a solid line (c) in FIG. In the experiment
In the case of the Ar gas pressure of 1 × 10 ⁻³ Torr and the Al target, abnormal discharge occurred at 500 V in the conventional configuration of FIG. 4, but in the configuration of the present invention shown in FIG. And stable sputtering at 1000V.

Next, the stabilization of ion energy control by the ECR plasma flow will be described with reference to FIG. In the ECR plasma method, the plasma is continuously accelerated and transported by the electric field in the plasma flow generated in the plasma flow and the plasma sheath electric field generated on the sample surface. The electric field in the plasma flow is 10 to 40 V, and is controlled by gas pressure, microwave power, and the like. Also,
The plasma sheath electric field is approximately 10V. For this reason,
By controlling the gas pressure, microwave power, and the like, an appropriate energy of 10 to 50 eV for film formation can be applied to transport ions from the plasma generation chamber 1 to the sample surface. In the conventional structure shown in FIG. 4, since the sputtering electric field extends over the entire plasma flow 5, the condition of low energy ion transport, which is a feature of such an ECR plasma method, is disturbed, which adversely affects film formation. Furthermore, since the sputtering electric field also reaches the inside of the plasma generation chamber 1 via the plasma flow 5, it also affects the plasma generation by ECR. On the other hand, in the configuration shown in FIG.
Since it is limited to 5A and does not affect the cylindrical plasma flow 5B irradiating the sample and the plasma generation chamber 1, the ion energy can be stably and reliably controlled independently of sputtering.

Next, stabilization of microwave introduction will be described with reference to FIG. The sputtered particles fly with a certain distribution from the target. In the ECR method, some of the sputtered particles are ionized by collision with circularly moving electrons in the plasma flow, and are transported toward the sample stage by the effect of the electric field in the plasma flow. However, the non-ionized particles fly straight from the target, and a part of the particles adheres to the microwave introduction window. If the deposited film exhibits metallic properties, microwaves are reflected here, making it difficult to introduce microwaves into the plasma chamber, making plasma generation unstable or impossible. In the conventional structure shown in FIG. 4, the target 15 is arranged so as to be in contact with the plasma flow 5 so that ions for sputtering can be easily obtained, so that the microwave introduction window 3 can be viewed directly from the target surface. On the other hand, in the configuration of the present invention shown in FIG. 2, the microwave introduction window 3 cannot be directly viewed from the target 15 due to the presence of the plasma blocking unit 6C. Therefore, particles flying from the target to the microwave introduction window can be removed, and sputtering can be performed without affecting the microwave introduction.

In the above description, the case where the electron cyclotron resonance plasma is used has been described in both the conventional example and the embodiment of the present invention. However, the same effects can be obtained by applying the present invention to other plasma generation methods, for example, when using microwave discharge plasma, high-frequency discharge plasma, or DC discharge plasma.
From the plasma in contact with the sputtering target, the ions in the plasma can be stably and reliably used by controlling the energy with high precision. In the above description, DC sputtering has been described as an example. However, the present invention can be applied to a case where high-frequency sputtering in which a high-frequency electric field is applied to a target to perform sputtering is used. Further, in the present invention, the case where the present invention is used for forming a film by sputtering a solid target is described, but the present invention can also be applied to a metal ion source using sputtering.

[Effects of the Invention] As described above, according to the present invention, in a plasma deposition apparatus that extracts ions generated in a plasma chamber, guides the ions to a target, and performs sputtering, the plasma to be applied to the target and the plasma to be applied to the sample substrate. Can be formed stably, with high reliability and controllability. Furthermore, when the plasma deposition apparatus of the present invention is applied to the manufacture of electronic components such as semiconductors, high quality electronic components can be realized without damaging the substrate. Furthermore, the present invention can be applied not only to the field of manufacturing electronic components but also to the formation of thin films on various materials, and the effect is great.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of the plasma deposition apparatus of the present invention, FIG. 2 is a schematic view showing the arrangement of a target, a plasma extraction window, and a microwave introduction window in the present invention, and FIG. FIG. 4 is a sectional view of a conventional plasma deposition apparatus. 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 table,
9: exhaust system, 10: magnetic coil, 11: magnetic shield, 12: first gas introduction system, 13: second gas introduction system, 14
... cooling water piping, 15 ... sputtering target,
16 ... Soft iron ring for local magnetic field, 17 ... Shield electrode, 18
…… Cooling water piping, 19 …… Sputter power supply.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 14/34-14/44 H01L 21 / 31,21 / 285

Claims (5)

(57) [Claims] 1. A plasma generation chamber for generating plasma by introducing a gas, a sample chamber in which a sample stage on which a sample substrate on which a film is to be formed is arranged is disposed, and a plasma chamber is provided between the plasma generation chamber and the sample chamber. A plasma extraction window for introducing plasma from the plasma generation chamber into the sample chamber as a plasma flow, and a target formed of a sputtering material and surrounding the plasma flow and arranged to be in contact with the plasma flow. In a plasma deposition apparatus, ions for sputtering the target are extracted from a part of the plasma flow and incident on the target, and a thin film is deposited and deposited on a sample substrate by sputtering the target. The plasma shielding chamber has an opening at the center and an outer periphery smaller than the inner periphery of the plasma generation chamber. By parts is fixed to the plasma generation chamber, the plasma deposition apparatus characterized by having a structure for dividing the plasma flow and plasma flow is directed to the sample stage, in the plasma flow is directed to the target. 2. The plasma deposition apparatus according to claim 1, wherein the plasma generation chamber has a microwave introduction window made of a material that allows microwaves to pass therethrough, the microwave generation window having a structure that shuts off the plasma generation chamber from the atmosphere and maintains a vacuum. A plasma deposition apparatus, wherein the plasma is generated by using electron cyclotron resonance discharge by microwave. 3. The plasma deposition apparatus according to claim 2, wherein the target is arranged at a position that cannot be directly seen from the microwave introduction window. 4. A plasma deposition apparatus according to claim 1, wherein the divergent magnetic field has a magnetic field distribution in which the magnetic field intensity decreases with an appropriate gradient from the plasma generation chamber toward the sample chamber. A plasma deposition device having a magnetic coil. 5. The plasma deposition apparatus according to claim 1, wherein said sample stage and said plasma generation chamber are electrically insulated.