JP2002343721A - Plasma generating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide plasma generating equipment wherein formation of a uniform deposition film and plasma treatment are enabled effectively, in formation of a deposition film on a large area substrate and various kinds of plasma treatment. SOLUTION: Plasma is generated effectively by using not an ordinary coil which generates plasma on the inside but a means which generates plasma effectively outside a coil. Thereby the coil is flattened, and wavelength of a high frequency and electric length of one turn of the coil are made almost identical in order to generate a high frequency magnetic field intensely outside the coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a low pressure plasma generation system and method. In particular, the present invention relates to an apparatus for generating a very uniform planar plasma that can be used to process semiconductor wafers in low pressure processing equipment.

[0002]

2. Description of the Related Art In recent years, various processes such as CVD, etching, and sputtering using plasma have been industrially put into practical use in manufacturing processes of semiconductor devices and the like. In particular, a plasma process and apparatus using a high frequency of 13.56 MHz are widely used because the substrate material can be processed regardless of a conductor or an insulator.

[0003] Among them, a plasma process using inductive coupling, in which low-energy high-density plasma can be easily obtained, damage to the substrate from the plasma is reduced, and an improvement in processing speed is expected, has attracted attention. . Against this background, various forms of inductively coupled plasma have been proposed. In general inductively coupled plasma, a dielectric tube is inserted into a high-frequency coil to generate plasma therein.

On the other hand, as a device for generating plasma outside the high-frequency coil, there is a plasma generator as disclosed in Japanese Patent Application Laid-Open No. Hei 6-84811. This plasma generator will be briefly described with reference to FIG. According to Japanese Patent Application Laid-Open No. 6-84811, in FIG. 3, the main coil 18 having flat side portions and the capacitor 12 forming a tuning circuit having high frequency energy coupled by high frequency matching by the high frequency generator 23 are connected. Prepare. A process chamber 30 having a quartz window 36 and containing a low-pressure gas is adjacent to the flat formed side of the main coil having an axis parallel to the quartz window surface, and has a circular disk-shaped two-dimensional planar plasma 2.
2 is formed and maintained by the high rate of change of the current flowing in the main coil. An electrode 38 located in the chamber and facing the window is used to mount a semiconductor wafer 44 to be processed, and the potential applied to this electrode separates the ion energy of the ions attracted and accelerated by the plasma. To be controlled.

[0005]

However, in the plasma generator described in Japanese Patent Laid-Open No. 6-84811,
Typically, a high-frequency induction magnetic field of 13.56 MHz is used, and this point is basically the same as the case where plasma is generated inside the coil. The difference between the plasma generator and the ordinary inductively coupled plasma that generates plasma inside the coil is mainly that a part of the coil is flattened and the plasma is generated outside the coil so as to easily cope with a wafer process. I am trying to make it happen. Usually, such a high-frequency coil is efficient in forming a high-frequency induction magnetic field inside the coil, but is not efficient in forming an external high-frequency induction magnetic field.

The fact that the formation of an external magnetic field in a normal coil is inefficient is briefly described with reference to FIG. FIGS. 2A and 2B show a current flowing in a simple one-turn rectangular coil and a magnetic field generated by the current. In FIG. 2A, the high-frequency current generated from the high-frequency power supply 1 is applied to the circuit shown in FIGS.
The current flows in the directions of the currents I ₁ and I _{2 shown} in FIG. At this time, the directions of the magnetic fields B ₁ and B ₂ generated by the currents I ₁ and I ₂ are the same inside the coil as shown in FIG. 2A, and the magnetic fields are strengthened. For this reason, the current that normally flows through the coil can generate a strong magnetic field inside the coil. On the other hand, currents I ₁ and I ₂ flowing through the coils are generated by magnetic fields B ₁ and B ₂ generated outside the coils.
Is shown in FIG. Outside the coil, the magnetic field B
₁ and B ₂ are in opposite directions to each other, and the combined magnetic field is weakened.

It is a main object of the present invention to solve the above-mentioned problems in the prior art and to provide a plasma generator for efficiently and uniformly generating inductively coupled plasma.

[0008]

Means for Solving the Problems A plasma generator according to the present invention which achieves the above object is as follows.
That is, the plasma generator of the present invention is a container capable of decompression, at least part of which is partitioned by a substantially flat electrically insulating window,
Introduction means for introducing a plurality of types of process gases into the container;
A control means for controlling the pressure of the process gas; a coil mounted outside the vicinity of the container and close to the insulating window, the axis of which is arranged substantially parallel to the insulating window; And a coupling means for coupling and flowing a current, wherein a planar plasma is formed and maintained parallel to the insulating window.In the plasma generator, the wavelength of the high frequency generated by the high frequency power supply is substantially It corresponds to one turn of the coil.

[0009] The side of the coil proximate the window is formed flat to improve the coupling between the coil and the plasma.

The phase is adjusted so that the maximum value of the high-frequency current is obtained substantially at the center of the flat portion formed on the side of the coil.

The frequency of the high frequency power is 100 to 600
MHz.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The present invention is a method for strengthening a high-frequency magnetic field outside a coil. As described above with reference to FIG. 2, the high-frequency induction magnetic field generated from the high-frequency coil can generate a strong high-frequency magnetic field inside the coil, but the magnetic field generated by the high-frequency current flowing through the coil outside the coil is It turns out that almost no effective external magnetic field can be formed.

Therefore, the present invention has studied a method for efficiently forming a strong magnetic field outside the coil. The result will be described with reference to FIG. FIGS. 3A and 3B show a current flowing through a one-turn simple rectangular coil and a magnetic field generated by the current. In FIGS. 3A and 3B, the high-frequency current generated from the high-frequency power supply 1 has a certain period of time when one turn of the coil is substantially equal to the wavelength of the high-frequency current. current shown in b)
It flows in the directions of I ₁ and I ₂ . At this time, the directions of the magnetic fields B ₁ and B ₂ generated by the currents I ₁ and I ₂ are the same as those in FIG.
As shown in (a), it is the same, and the magnetic fields are weakened. On the other hand, the directions of the magnetic fields B ₁ and B ₂ generated outside the coil by the currents I ₁ and I ₂ flowing through the coil are shown in FIG. Outside the coil, the magnetic fields B ₁ and B ₂ are in the same direction as each other, and the combined magnetic field is strong. Thus, one of the coils
By setting the length of the turn to be substantially equal to the wavelength of the high frequency, the external magnetic field can be strengthened, and the high frequency power can be efficiently supplied to the plasma outside the coil. FIG. 4 shows the strength of the magnetic field at this time. FIG. 4A plots the magnetic field intensity generated in the coils shown in FIGS. 2 and 3 with respect to the position. The positions of 1 and -1 on the horizontal axis correspond to portions where the current of the coil flows, respectively. In the conventional one, the magnetic field strength is large at the position corresponding to the inside of the coil between -1 and 1, but at the portion of 1 or more and outside the coil of -1 or less, the magnetic field strength rapidly decreases as the distance from the coil increases. I have. On the contrary, it can be seen that the magnetic field strength according to the present invention is higher outside than the conventional one. FIG. 4B shows a case where the number of turns of the coil is set to seven. It can be seen that as the number of turns increases, the difference between the strength of the conventional external magnetic field and the strength of the external magnetic field of the present invention further increases.

The frequency of the high frequency power used in the plasma generator of the present invention is preferably in the range of 100 to 600 MHz in consideration of the substrate size required in a normal plasma process.

The plasma generator shown in FIG. 1 is an example of the plasma generator of the present invention. In FIG. 1, reference numeral 12 denotes a reaction vessel. A substrate holder is arranged in the reaction vessel. 5 is a substrate arranged on the substrate holder (6). A heater (not shown) is provided inside the substrate holder (6) so that the substrate (5) can be heated. The high frequency power is the high frequency power (1
It is generated in 1), divided through a matching circuit (10), and supplied to one end of a high-frequency coil (3). As described above, the high-frequency coil has a length of one turn substantially equal to the wavelength of the high-frequency wave substantially in accordance with the frequency of the supplied high-frequency power. Accordingly, it has a flat coil of several turns. The high-frequency coil (3) is isolated from the discharge space via a dielectric member (4) constituting a part of the reaction vessel (12). The gas is exhausted by a vacuum exhaust means (9) equipped with a vacuum pump via an exhaust pipe equipped with an exhaust valve. Reference numeral 8 denotes a plasma generation gas supply system including a gas cylinder, a mass flow controller, a valve, and the like. When this apparatus is used, for example, as a plasma CVD apparatus, plasma CVD is performed as follows. After the reaction vessel (12) is evacuated to a high vacuum by the exhaust mechanism (9), a raw material gas is introduced into the reaction vessel (12) from the gas supply means (8) and maintained at a predetermined pressure. In such a case, high-frequency power is supplied from the high-frequency power supply (11) to the high-frequency coil (3) via the matching circuit (10), and plasma is generated between the high-frequency coil (3) and the substrate (5). By doing so, the source gas is decomposed and excited by the plasma, and a deposited film is formed on the deposition target substrate (5).

In the present invention, any known dielectric material can be selected for the dielectric member (4), but a material having a small dielectric loss is preferable, and a material having a dielectric loss tangent of 0.01 or less is preferable. , More preferably 0.001 or less. For polymer dielectric materials, polytetrafluoroethylene,
Polyethylene trifluoride, polyfluoroethylene propylene, polyimide, and the like are preferable. For glass materials, quartz glass, borosilicate glass, and the like are preferable. For porcelain materials, boron nitride, silicon nitride, aluminum nitride, and the like, aluminum oxide, and magnesium oxide A porcelain mainly containing one or more element oxides among element oxides such as silicon oxide is preferable. In the present invention, the frequency of the high frequency power supply (11) is preferably 100 to 600 MHz.
It is desirable to set the range of z.

In the present invention, the purpose of using the plasma generator is not limited to the above-described plasma CVD, but may be another plasma process, that is, plasma etching, sputtering, or the like.

The plasma generator of the present invention is
When used as a D apparatus, as a gas to be used, a known source gas that contributes to film formation is appropriately selected and used depending on the type of a deposited film to be formed. For example, in the case of forming an a-Si based deposited film, silane, disilane,
Higher order silane and the like or a mixed gas thereof may be mentioned as a preferable raw material gas. In the case of forming another deposited film, for example, a raw material gas such as germane, methane, or ethylene, or a mixed gas thereof may be used. In any case, the source gas for film formation can be introduced into the reaction vessel together with the carrier gas. Examples of the carrier gas include a hydrogen gas and an inert gas such as an argon gas and a helium gas.

It is also possible to use a gas for improving characteristics such as adjusting the band gap of the deposited film. Examples of such a gas include a gas containing a nitrogen atom such as nitrogen and ammonia; a gas containing an oxygen atom such as oxygen, nitric oxide and nitrous oxide; a hydrocarbon gas such as methane, ethane, ethylene, acetylene, and propane; Silicon fluoride, disilicon hexafluoride,
A gaseous fluorine compound such as germanium tetrafluoride or a mixed gas thereof may be used.

A doping gas can be used for doping the deposited film to be formed. Examples of such a doping gas include gaseous diborane, boron fluoride, phosphine, and phosphorus fluoride.

The substrate temperature at the time of forming the deposited film can be set as appropriate. However, when an amorphous silicon-based deposited film is formed, the temperature is preferably from 60 ° C. to 400 ° C., more preferably from 100 ° C. to 350 ° C. It is desirable that

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

This embodiment shows an example in which amorphous silicon is formed by a plasma CVD process using the plasma generator shown in FIG. Plasma C of this embodiment
The VD process is 300mm long, 400mm wide, thickness l
A glass substrate having a thickness of 5 mm was formed in a reaction vessel. The coil is formed by bending an Al sheet having a width of 40 mm and a thickness of 1 mm, and 450 m parallel to the dielectric window so that the length per turn is 1000 mm.
m, the length of 5 turns 400 mm vertically set to 50 mm,
A rectangular spiral coil having a width of 450 mm and a height of 50 mm was used. In this study, the frequency was set to 300 MHz, and a study was conducted in the following procedure using a high-frequency power source having a variable frequency.

First, the inside of the reaction vessel (12) is evacuated (9).
To evacuate, and the inside of the reaction vessel (12) is 1 × 10 ⁻⁶ T
The pressure was adjusted to orr. Then, a substrate heating heater (not shown) is energized and the film formation substrate (6) is heated to 250 ° C.
And kept at a temperature of. Then, a film was formed in the following procedure. That is, SiH ₄ gas is introduced into the reaction vessel (12) at a flow rate of 1000 sccm from the raw material gas supply means (8) through the gas release pipe (14), and the inside of the reaction vessel is reduced to 1%.
The pressure was adjusted to 0 mTorr. Under such circumstances, a high frequency power of 11 MHz was generated by the high frequency power supply (11) at 4 KW, and the high frequency was supplied to the high frequency coil (3) via the matching circuit (10). The matching circuit (10)
It was adjusted appropriately according to the frequency of the high frequency power supply. Thus, an amorphous silicon film was formed on the cylindrical deposition target substrate (5).

The film quality and film quality distribution, the deposition rate distribution and the deposition rate distribution of the amorphous silicon film formed as described above were evaluated by the following methods.

The film quality and the film quality distribution are as follows: A line is drawn about every 30 mm in the vertical direction of the substrate on which the amorphous silicon film is formed, and a line is drawn about every 40 mm in the horizontal direction. Ratio ((photoconductivity σp)
/ (Dark conductivity σd)).
Here, the photoconductivity σp is H at an intensity of 1 mW / cm ^2.
The evaluation was made based on the conductivity at the time of irradiation with an e-Ne laser (wavelength 632.8 nm). According to the inventor's findings so far, an amorphous silicon film used for a solar cell or a thin film transistor has no doping and is capable of obtaining a deposited film having a light / dark conductivity ratio of 10 ³ or more by the above method. It is at a level where device creation is possible based on optimization. However, due to the recent high performance,
A material having a dark conductivity ratio of 10 ⁴ or more has become indispensable, and it is expected that a light / dark conductivity ratio of 10 ⁵ or more will be required in the near future. From such a viewpoint, in this experiment, the value of the light / dark conductivity ratio was evaluated based on the following criteria.

A: The light / dark conductivity ratio is 10 ⁵ or more,
Very good film properties.

：: The light / dark conductivity ratio is 10 ⁴ or more,
Good film properties.

Δ: The light / dark conductivity ratio is 10 ³ or more,
No problem in practical use.

×: The light / dark conductivity ratio is less than 10 ³ ,
Not practical.

Evaluation of the deposition rate and the distribution of the deposition rate
The film thickness is measured using an eddy current film thickness meter (manufactured by Kett Scientific Research Institute) at 100 locations on the substrate on which the Si film is formed in the same manner as the above-described measurement position of the light / dark conductivity ratio. Was evaluated. The deposition rate was calculated based on the film thickness at 100 locations, and the average of the obtained values was defined as the average deposition rate. Evaluation of the deposition rate distribution was performed as follows.
That is, as for the deposition rate distribution, the difference between the maximum value and the minimum value of the deposition rate at 100 locations is obtained, and the difference is divided by the average deposition rate at 100 locations to obtain the deposition rate distribution ｛(maximum value−minimum value) / average. The value｝ was determined and expressed as a percentage as the axial deposition rate distribution.

As a result, the obtained deposition rate distribution was 4%, and the light / dark conductivity ratio was 1 × 10 ^{5 at} all measurement points.
３3 × 10 ⁵ , and an amorphous silicon film having uniform and excellent characteristics was obtained.

As a comparison with the above embodiment, 13.56M
An attempt was made to generate plasma under the same conditions using high-frequency power of Hz and similar coils, but no plasma was generated.

[0035]

As described above, according to the present invention,
It is possible to efficiently generate a very uniform planar plasma at a low pressure. Therefore, according to the present invention, a large-area, high-quality semiconductor device can be efficiently manufactured by forming a thin film by a plasma process, forming a fine pattern by etching, or the like.

[Brief description of the drawings]

FIG. 1 is a compound diagram showing one example of a plasma generator of the present invention.

FIG. 2 is a compound diagram for explaining a current and a magnetic field of a coil used in a conventional plasma generator.

FIG. 3 is a compound diagram for explaining a current and a magnetic field of a coil used in the plasma generator of the present invention.

FIG. 4 is a graph showing a magnetic field intensity distribution generated in the present invention and a conventional plasma generator.

FIG. 5 is a compound diagram showing a conventional plasma generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma 2 Dielectric plate 3 High frequency coil 4 Dielectric member 5 Substrate 6 Substrate holder 8 Gas supply means 9 Vacuum exhaust means 10 Matching circuit 11 High frequency power supply 12 Reaction vessel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05H 1/46 H01L 21/302 BF Term (Reference) 4G075 AA24 AA30 AA62 BA01 BC02 BC04 BC06 CA02 CA13 CA25 CA47 CA51 CA63 CA65 DA02 DA18 EA06 EB01 EB41 EC13 EE07 EE12 FB01 FB06 FB12 FC15 4K030 CA04 CA12 FA04 JA09 JA18 JA19 KA30 KA41 4K057 DA16 DB06 DD01 DM02 DM16 DM33 DM37 DM38 DN01 5F004 AA01 BA20 BB11 BD04 AC05 AD04 AC05 AC04 AD06 AD07 AD08 AF07 BB02 CA13 DP03 EC01 EC05 EH04 EH11

Claims (4)

[Claims] 1. A pressure-reducing container at least partially partitioned by a substantially flat electrically insulating window, an introduction unit for introducing a plurality of types of process gases into the container, and a control unit for controlling the pressure of the process gas. And a coil mounted near the insulating window outside the vicinity of the container and having its axis substantially parallel to the insulating window, and coupling means for coupling a high-frequency power supply to the coil to flow current. Wherein a planar plasma is formed and maintained in parallel with the insulating window, wherein the wavelength of the high frequency generated by the high frequency power supply substantially corresponds to one turn of the coil. A plasma generator characterized by the above-mentioned. 2. The side of the coil adjacent to the window,
2. The plasma generating apparatus according to claim 1, wherein the plasma generating apparatus is formed to be flat and improves a coupling between the coil and the plasma. 3. The high-frequency plasma generator according to claim 2, wherein the phase is adjusted so that the maximum value of the high-frequency current is obtained substantially at the center of the flat portion formed on the side of the coil. 4. The frequency of the high-frequency power is 100 to 60.
4. The method according to claim 1, wherein the frequency range is 0 MHz.
2. The high-frequency plasma generator according to claim 1.