JP5484375B2 - Plasma film forming apparatus and plasma film forming method - Google Patents

Description

  The present invention relates to a plasma film forming apparatus and a plasma film forming method.

  A plasma film forming apparatus is widely used as an apparatus for forming a thin film such as an amorphous silicon thin film or a microcrystalline silicon thin film on a substrate. Nowadays, for example, a plasma film forming apparatus capable of forming a meter-sized large-area thin film at a high speed at a time, such as a power generation layer of a thin film silicon solar cell or a thin film transistor used in a flat display panel, has been developed. . In order to form a silicon thin film having a large area, it is common to use a parallel plate type plasma film forming apparatus.

The parallel plate type plasma film forming apparatus has two electrodes facing each other with a distance of several mm to several tens mm in the vacuum chamber. These two electrodes are installed in a horizontal plane, supply high-frequency power to one electrode, and the other electrode is grounded. In the case of forming a silicon thin film, a film forming gas such as silane (SiH ₄ ) or hydrogen (H ₂ ) is supplied to a gap region between the electrodes serving as a discharge space through a large number of gas holes provided in one electrode. . The gas supplied to the discharge space is turned into plasma by high frequency power. The deposition gas is decomposed in the plasma, becomes radicals and ions, and enters the deposition target substrate to form a silicon film on the substrate. In general, the other electrode on the grounded side is used as a stage, and a deposition target substrate is placed on the other electrode.

  On the other hand, in recent years, VHF plasma generated using high frequency power in the VHF (Very High Frequency) band having a frequency higher than that of the conventional 13.56 MHz is used to meet the needs for improving film formation quality and film formation speed. It has been actively studied for use in film formation. Since VHF plasma has the characteristics of high density and low electron temperature, it is expected as a solution to the above needs.

  However, when the frequency of the high-frequency power increases, the property of the high-frequency power as a “wave” appears remarkably, and the film forming characteristics tend to be non-uniform in the electrode plane. That is, when the frequency of the high-frequency power increases, the high-frequency power causes interference in the electrode plane, and the electric field strength distribution becomes non-uniform by forming a standing wave, resulting in non-uniform plasma density. The film forming speed and film quality itself tend to be non-uniform. In recent meter-sized substrates (1.1 m × 1.4 m), this tendency becomes a prominent factor, which is a big problem in practical use.

  For these problems, Patent Document 1 discloses that in a plasma processing apparatus that generates plasma between an electrode for applying a high frequency and an electrode on which a substrate is placed, high frequency power is supplied from a plurality of locations to the electrode to which the high frequency is applied. How to do is described. Specifically, the high-frequency power supplied to the four left and right sides of the electrode is generated so as to be two types of pulse variable outputs that are time-divided so as not to interfere with each other, and is relative to the pulse modulation output. A phase difference is provided. Thus, according to Patent Document 1, the electric field strength distribution when high-frequency power is supplied to two of the four locations and the electric field strength distribution when high-frequency power is supplied only to the other are overlapped and time averaged. The obtained electric field strength distribution can be obtained, and it is said that the uniformity of the plasma over the entire surface of the large area substrate (the length and width of 1 m × 1 m or more) can be improved.

JP 2006-216679 A

  In the plasma processing apparatus described in Patent Document 1, high-frequency power feeding to the four power supply locations of the electrode is switched in a pulse manner alternately on the left and right sides of the electrode (two locations on the right side with respect to the left two locations), and each pulse By providing a relative phase difference to the output, the electric field distributions are overlapped and uniformed in time average.

  However, since the frequency of the high frequency described in Patent Document 1 is 27.12 MHz, the influence of the standing wave becomes significant in the higher frequency VHF band, and it is estimated that it is difficult to equalize.

  Therefore, the present inventors tried to verify the homogenization using 60 MHz VHF in the configuration of the plasma processing apparatus described in Patent Document 1. As a result, when the location where the high frequency is fed is switched over time to provide a phase difference, the electric field distribution certainly changes, but when plasma is generated, the plasma distribution does not change to the desired distribution. The details of verification and the cause of the failure will be described in the embodiments described later.

  Thus, it is difficult to obtain uniform plasma when a high-frequency power in the VHF band is supplied using the plasma processing apparatus described in Patent Document 1 and a meter-sized substrate (substrate to be processed) is processed. It is.

  The present invention has been made in view of the above, and a plasma film forming apparatus and a plasma capable of obtaining uniform plasma even when a substrate to be processed having a large area is processed by supplying high-frequency power in the VHF band. It aims at obtaining the film-forming method.

  In order to solve the above-described problems and achieve the object, a plasma film forming apparatus according to one aspect of the present invention includes a vacuum chamber and a first electrode, and a film forming chamber is formed in the film forming chamber. A deposition target substrate is placed on a second electrode disposed to face the first electrode, and deposition is performed using plasma generated between the first electrode and the second electrode. The second main surface of the first electrode opposite to the first main surface facing the second electrode has a plurality of feeding points, and the plurality of feeding points are provided. Each of the feeding points is supplied with pulse-modulated high-frequency power, and the pulse at the high frequency has a first power in a first period in the on time and continues to the first period in the on time. Having a second power in a second period, wherein the first power is the second power. Characterized in that more than 5% higher.

  According to the present invention, since the plasma can be reliably formed by increasing the initial high-frequency power of the pulse from the remaining period, a desired plasma distribution can be obtained even when the pulse repetition frequency is increased. Thereby, even when a substrate having a large area is processed by supplying high-frequency power in the VHF band, uniform plasma can be obtained.

FIG. 1 is a cross-sectional view illustrating a plasma processing apparatus according to an embodiment. FIG. 2 is a high-frequency power supply system diagram according to the embodiment. FIG. 3 is a sequence diagram showing the relationship between the high frequency power and the phase amount in the prior art. FIG. 4 is a diagram showing a plasma distribution formed between an electrode and a stage in the prior art. FIG. 5 is a sequence diagram illustrating a relationship between high-frequency power and a phase amount according to the embodiment. FIG. 6 is a diagram showing a plasma distribution formed between the electrode and the stage according to the embodiment. FIG. 7 is a sequence diagram illustrating the relationship between the high-frequency power and the phase amount in the embodiment. FIG. 8 is a diagram showing a plasma distribution formed between the electrode and the stage in the embodiment. FIG. 9 is a diagram showing a plasma distribution formed between the electrode and the stage in the embodiment.

  Embodiments of a plasma film forming apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
The structure of the plasma film-forming apparatus 100 concerning embodiment is demonstrated using FIG. FIG. 1 is a cross-sectional view schematically showing a configuration of a plasma film forming apparatus 100 according to an embodiment.

  As shown in FIG. 1, a plasma film forming apparatus 100 includes a vacuum chamber 1, an exhaust port 3, a film forming chamber 8, an insulating flange 4, an electrode (first electrode) 5, a gas supply port 6, a shower plate 7, a stage. (Second electrode) 2 and a plurality of high-frequency power supplies 10a to 10d (see FIG. 2).

  The vacuum chamber 1 forms side portions and bottom portions on the outer wall of the plasma film forming apparatus 100, and extends so as to cover the side portions and bottom portion of the film forming chamber 8.

  The exhaust port 3 communicates with the inside of the vacuum chamber 1 (film forming chamber 8) and is connected to a vacuum pump (not shown) via an exhaust pipe (not shown). It is provided to evacuate with a vacuum pump.

  The film forming chamber 8 is a space formed by being covered with the electrode 5 and the vacuum chamber 1. In the film forming chamber 8, plasma is generated as described later.

  The insulating flange 4 insulates the electrode 5 from the vacuum chamber 1 in terms of high-frequency power and vacuum-seals the electrode 5 from the vacuum chamber 1. Thereby, the film forming chamber 8 is a space that can be evacuated.

  The electrode 5 forms an upper part of the outer wall of the plasma film forming apparatus 100 and extends to cover the upper part of the film forming chamber 8. Further, the electrode 5 extends so as to cover, for example, the upper part and the side part of the film forming chamber 8. A plurality of high-frequency power supplies 10a to 10d (see FIG. 2) are connected to the electrode 5.

  The gas supply port 6 is connected to a gas supply source (not shown) via a gas supply pipe (not shown), and a film forming gas is supplied from the gas supply source to the space between the electrode 5 and the shower plate 7. Is provided to supply.

  The shower plate 7 has a plurality of gas holes, and a film forming gas is introduced into the film forming chamber 8 through the gas holes.

  The stage 2 is disposed so as to face the first main surface 5 a of the electrode 5 in the film forming chamber 8 and is grounded, for example, and functions as a counter electrode (second electrode) with respect to the electrode 5. In addition, a deposition target substrate 9 is placed on the stage 2.

  As shown in FIG. 2, the plurality of high-frequency power supplies 10 a to 10 d are connected to two positions in the vicinity of the left and right ends of the second main surface 5 b of the electrode 5 (a total of four positions). Supply. The second main surface 5b is a surface on the opposite side of the first main surface 5a facing the stage 2 in the electrode 5.

  In the plasma film forming apparatus 100, the film forming gas supplied from the gas supply port 6 is introduced into the film forming chamber 8 through the plurality of gas holes of the shower plate 7, and the pressure in the film forming chamber 8 is reduced to a vacuum pump (see FIG. (Not shown). When a high frequency is applied to the electrode 5 from the plurality of high frequency power supplies 10 a to 10 d in this state, plasma is generated between the electrode 5 and the stage 2 and a thin film is deposited on the deposition target substrate 9.

  Next, a method of supplying high-frequency power to the electrode 5 applied to the plasma film forming apparatus 100 will be described with reference to FIG. FIG. 2 is a diagram showing a power supply system / configuration of a plurality of high frequency power supplies 10a to 10d for supplying high frequency power to the electrode 5 in the plasma film forming apparatus.

  In FIG. 2, as an example, the electrode 5 is rectangular, the size of the shower plate 7 facing the stage 2 is 1.2 m × 1.5 m, and high-frequency power is supplied from the atmosphere side opposite to the film forming chamber 8 side. The configuration is shown when doing so. For example, a 60 MHz VHF band is used as the frequency of power to be fed in order to realize high-speed film formation.

  First, both short sides 5b1 and 5b2 are considered as two opposite sides on the second main surface 5b of the electrode 5. A method of supplying high frequency power in the VHF band to the electrode 5 from both short sides 5b1 and 5b2 will be described.

  High-frequency power feed points 27 a and 27 b are provided on the short side 5 b 1 side of the electrode 5, and high-frequency power feed points 27 c and 27 d are provided on the short side 5 b 2 side of the electrode 5. In other words, the electrode 5 has a rectangular shape, and the second main surface 5b has a plurality of feeding points (a plurality of feeding points) arranged on one side (short side 5b1) of the two opposite sides in the square. First feeding points) 27a and 27b, and a plurality of feeding points (a plurality of second feeding points) 27c and 27d arranged on the other side (short side 5b2) of the two opposite sides.

  Matchers 26a, 26b, 26c, and 26d that adjust the matching state of the high-frequency power are connected to the feeding points 27a, 27b, 27c, and 27d, respectively. For connection from the matchers 26a to 26d to the feeding points 27a to 27d, a metal plate or rod having good conductivity (not shown) or a high-frequency coaxial cable is used. Each of the four feeding points 27a to 27d is set in a region close to the electrode periphery.

  The matchers 26a, 26b, 26c and 26d are fed with the high frequency power amplified by the high frequency amplifiers 25a, 25b, 25c and 25d, respectively.

  The signal generator 21 generates a VHF signal (for example, a 60 MHz sine wave) and supplies it to the distributor 22. The distributor 22 distributes a VHF signal (for example, a 60 MHz sine wave) into, for example, four power signals and supplies the power signal to the phase shifter 23.

  The phase shifter 23 adjusts the phase of each of the four signals. That is, the phase shifter 23 includes four phase adjustment units 23a to 23d corresponding to the four signals. The four phase adjustment units 23a to 23d receive the four signals and adjust the phase. Each of the phase adjusters 23a to 23d supplies the adjusted signal to the corresponding on / off switch 24a to 24d.

  The on / off switchers 24a, 24b, 24c, and 24d pulse the output signal from the phase shifter 23 and output the high-frequency signal to the corresponding high-frequency amplifiers 25a, 25b, 25c, and 25d. The high frequency amplifiers 25a, 25b, 25c, and 25d amplify the input high frequency signal and output it as high frequency power.

  The phase control (phase adjustment) in the phase shifter 23 may be controlled by a controller (not shown). Alternatively, the on / off switchers 24a to 24d may be controlled by inputting an on / off signal from a controller (not shown) in order to turn on / off the high frequency output. Alternatively, in some cases, the on / off switchers 24a to 24d do not perform the on / off operation and can be used as a continuous output.

  That is, each of the high frequency power supplies 10a to 10d is equivalent to the signal generator 21, the distributor 22, the phase shifter 23, the corresponding on / off switchers 24a to 24d, the corresponding high frequency amplifiers 25a to 25d, and the corresponding matcher. (Matcher) Functions as a power supply circuit having 26a to 26d. The plurality of high-frequency power supplies 10a to 10d supply high-frequency power in the VHF band to the plurality of power supply points 27a to 27d.

  The inventors of the present invention first verified the above-described problems of the prior art. The signal generator 21 generates a VHF signal (for example, a 60 MHz sine wave), and the phase shifter 23 sets the phase of the high-frequency power to be supplied to the feeding points 27a and 27b to the same feeding point 27c and 27d. The phase of the high frequency power to be supplied is set to + -60 degrees with respect to the phase of the high frequency power at the feeding points 27a and 27b. Also, the on / off switchers 24a to 24d are operated in the pulse sequence shown in FIG. 3, and the pulse duty (X in the figure) is set to 40% and the repetition frequency of 1 kHz (S in the figure) is set to 1 kHz. .

  In FIG. 3, (a) shows an on / off operation of a pulse to be fed to the feeding point 27a and the feeding point 27b. (B) indicates the phase amount during the on operation, and here, power is supplied with a phase amount of 0 °. On the other hand, (c) shows an on / off operation of a pulse to be fed to the feeding point 27c and the feeding point 27d, and (d) shows a phase amount during the on operation. In (D), the phase amount is supplied with power by alternately switching between + 60 ° and −60 ° in terms of time. When high-frequency power of 60 MHz is supplied from the high-frequency amplifiers 25a, 25b, 25c, and 25d by the above-described power supply sequence and phase control, there is a phase difference between the left and right power supply points 27a and 27b and the power supply points 27c and 27d of the electrode 5. VHFs with + 60 ° and −60 ° are fed alternately. As a result, an electric field distribution corresponding to the phase amount is formed between the electrode 5 and the stage 2 while changing at 1 KHz. The change amount (movement amount) of the electric field distribution due to the phase change in vacuum is about 167 cm at the phase amount + 60 ° to −60 ° at the frequency of 60 MHz.

Next, plasma generation by H ₂ gas was performed by feeding the VHF, and the distribution was evaluated. The plasma distribution was evaluated by applying a negative (−) voltage to an ion collection probe (not shown) embedded in the stage surface and measuring the ion current flowing from the plasma into the probe. The discharge conditions were an H ₂ flow rate of 1000 sccm, a pressure of 1000 Pa, an interval between the electrode and the stage of 5 mm, and a VHF power of 1000 W × 4 locations.

When plasma is generated under the above conditions, the standing wave distribution of the electric field formed between the electrode 5 and the stage 2 (the peak of the electric field distribution) corresponds to the time variation of the phase amount as described above. It is expected to be divided into left and right. However, as a result of the evaluation, as shown in FIG. 4, the distribution of the measured H ₂ plasma was generated in a localized manner in the center of the electrode without being separated into right and left in accordance with the electric field distribution. In the measurement of ion current, integration was performed for 1 second so that it could be sufficiently averaged for a repetition frequency of 1 KHz.

  The reason why the plasma is localized and distributed without corresponding to the electric field distribution is considered as follows. When high frequency is applied in a pulsed manner, the impedance between the electrodes is in an unloaded state (a state in which there is no plasma yet) until the discharge at the moment of application starts, so the electric field distribution corresponding to the phase amount is It is formed. Next, when discharge is started by the electric field formed between the electrodes and plasma is generated, the plasma is generated as an impedance load between the new electrodes. Therefore, the electric field formed between the electrodes in the initial no-load state changes to a re-formed distribution with respect to the impedance between the electrodes including the plasma load. The instantaneous electric field distribution is different from the initial electric field distribution, and therefore does not form a desired plasma distribution. Once the plasma is generated, the impedance load between the electrode and the stage is determined, so that the electric field distribution is stabilized and the plasma distribution is also determined.

  This phenomenon is caused by the fact that when a high frequency is applied in a pulsed manner, the impedance between the electrodes changes dynamically in the initial application of the pulse. When the pulse repetition frequency is as slow as about a second, the dynamic change in impedance at the initial stage of pulse application can be ignored. However, at a high speed of less than msec, the period during which the impedance occupying the pulse width changes dynamically cannot be ignored, and thus there is a problem that a desired plasma distribution cannot be obtained. Therefore, in the above-described verification experiment, the plasma distribution is distributed despite the fact that the high-frequency phase difference + -60 ° applied in a pulsed manner is changed at 1 KHz to change the position of the peak of the electric field distribution (the convex portion where the electric field is strong). Seems to have not changed significantly.

  As a result of such prior art, when the plasma distribution is made uniform by multiple power feeding to the electrodes, if the power feeding location and the phase of the VHF power are switched at high speed, the desired plasma change cannot be obtained and the uniformization is achieved. It is difficult.

  A power feeding method according to the present embodiment that solves the above problems will be described.

  First, the power feeding method shown in FIG. 5 according to the present embodiment will be described.

  FIG. 5 shows a method of feeding VHF to the feeding points 27a, 27b, 27c, and 27d. Rather than performing the pulsed VHF power supply at a constant power (the pulse height is constant), the VHF power is set higher than a predetermined value at the initial stage of the pulse, and the VHF power is supplied at a predetermined value during the remaining period of the pulse. .

  The initial power (H1 + H2) in the pulse shown in FIG. 5 is preferably higher by 5% or more than the steady-state power (H1) in the pulse.

  If the initial power (H1 + H2) is higher than the steady-state power (H1) in the pulse at a rate of less than 5%, the influence on the electric field formation due to the dynamic change of impedance becomes obvious and desired There is a tendency that plasma distribution cannot be obtained.

  Moreover, it is preferable that the period (W2) which makes electric power high is the period of the beginning 5% or more and 20% or less in the pulse width (W1), for example.

  If the period (W2) during which the power is increased is less than 5% of the pulse width (W1), the influence of the dynamic change of the impedance on the electric field formation becomes obvious, and the desired plasma distribution tends not to be obtained. . Or, if the period (W2) during which the power is increased is longer than 20% of the pulse width (W1), the plasma characteristics will be affected, and the desired plasma distribution tends to be not obtained.

  These values can be optimized depending on the discharge conditions.

  FIG. 6 shows the result of evaluation of plasma distribution using the power feeding method shown in FIG. 5 according to this embodiment. In this evaluation, the initial power (H1 + H2) shown in FIG. 5 was increased by 30% with respect to the steady-state power (H1). Further, the period (W2) to be increased is set to the first 10% in the pulse width (W1).

  As a result, as shown in FIG. 6, two plasma distributions were formed with the peaks (convex portions) of the distribution separated in the long side direction of the electrode. As described above, the plasma is generated in response to the change in the electric field distribution because the electric field is formed by the dynamic change of the impedance by applying the power (H2) higher than the steady VHF power (H1) at the initial stage of the pulse. This is thought to be because the impact on the environment can be reduced. The distance between the peaks of the distribution is about 80 cm, which is a small value with respect to the movement amount of the electric field distribution in the vacuum described above. This is a reduction in the wavelength of VHF propagating in the plasma (usually The shortening rate in the plasma is from 0.5 to 0.9). That is, it was confirmed that a uniform plasma distribution can be obtained as compared with the prior art.

  Next, the power feeding method shown in FIG. 7 according to the present embodiment will be described. The power supply method shown in FIG. 7 is the same as the power supply method shown in FIG. 5 in that the VHF power is set higher than a predetermined value at the initial stage of the pulse and the VHF power is set to a predetermined value during the remaining period of the pulse.

  FIG. 7 shows a relationship between a sequence and a phase in which VHF is supplied in a pulse manner to the electrode 5 from the four feeding points 27a, 27b, 27c, and 27d. There are three patterns (X), (Y), and (Z) for supplying power to the four places, which is one cycle (S). First, during the period (X), power is fed at the same phase of 0 ° at all four feeding points 27a to 27d. In the next period (Y), the feeding points 27a and 27b are fed with the same phase of 0 °, and the feeding points 27c and 27d are fed with the opposite phase of −180 °. In the last (Z) period, the feeding points 27a and 27c are fed with the same phase of 0 °, and the feeding points 27b and 27d are fed with the opposite phase of −180 °.

  One cycle of (X) to (Z) was repeated at 1 KHz, and each duty ratio in the periods (X), (Y), and (Z) was set to 30%. When plasma is generated by the above power supply method, the three patterns of plasma distribution shown in FIG. 8 are formed. In the period (X), since the four feeding points are fed in phase, a convex plasma distribution is formed at the center of the electrode. In the period (Y), since in-phase / reverse-phase power feeding is performed in the direction of the long side of the electrode, a distribution is formed in which the center of the electrode becomes a valley and the plasma becomes stronger on both sides of the short side. In the period (Z), since in-phase / reverse-phase power feeding is performed in the direction of the short side of the electrode, a distribution is formed in which the center of the electrode becomes a valley and the plasma becomes stronger from the center of the electrode to both sides of the long side.

  By repeating the three patterns (X), (Y), and (Z) shown in FIG. 7 at 1 KHz, the plasma distribution also changes in the three patterns (X), (Y), and (Z) shown in FIG. Generated while moving. As a result, the plasma distribution shown in FIG. 9 was obtained on a time average. In this case, the uniformity of the plasma distribution was 13% in a 1.4 m × 1.1 m region, and a uniform plasma could be generated over a large area. That is, it was confirmed that a more uniform plasma distribution can be obtained as compared with the prior art.

Next, the power supply method shown in FIG. 7 is applied to the plasma film forming apparatus 100 to generate high-frequency plasma with a mixed gas of silane gas (SiH ₄ ) and hydrogen gas (H ₂ ), and a large-area glass substrate. An experimental example in which a microcrystalline silicon film is deposited will be described.

In FIG. 1, a 1400 mm × 1100 mm glass substrate (thickness: 4 mm) was placed on the stage 2 as the deposition target substrate 9. The deposition target substrate 9 was heated to 200 ° C. using a sheath heater (not shown) built in the stage 2. Next, the height position of the stage 2 was adjusted so that the distance between the shower plate 7 and the deposition target substrate 9 was 10 mm. In this state, silane gas (SiH ₄ ) and hydrogen gas (H ₂ ) were supplied to the gas supply port 6 at flow rates of 1 slm and 50 slm, respectively, and the gas pressure in the film forming chamber 8 was adjusted to 1000 Pa. After the gas pressure was stabilized, high-frequency power in the VHF band 60 MHz was supplied to the electrode 5 from the high-frequency power supply system shown in FIG. 2 to generate a mixed plasma of silane (SiH ₄ ) / hydrogen (H ₂ ). The outputs of the high-frequency amplifiers 25a to 25d were 2000 W, respectively, and power was supplied to the power supply points 27a to 27d by the above-described power supply method shown in FIG.

  As a result of such an experiment, a silicon-based thin film of 2 μm was deposited on the glass substrate, and the in-plane film thickness distribution was within ± 15% of the average value. Assuming that the formed thin film is used for a solar cell, the crystallization rate of the film estimated by Raman spectroscopy is Ic / Ia = 7.2, which is suitable for a thin film solar cell using microcrystalline silicon. A crystalline silicon thin film was obtained.

  Note that the outputs of the high-frequency amplifiers 25a to 25d are not limited to the above-mentioned values, but can be made uniform by changing the respective output values corresponding to the process conditions (gas pressure, gas flow rate, distance between the electrode and the stage). Plasma distribution can be obtained.

  In this case, a plurality of feeding points 27a to 27d include a feeding point having a small steady state high frequency power H1 and a feeding point having a large steady state high frequency power H1. At this time, the feeding point where the steady state high frequency power H1 is small is higher than the feeding point where the steady state high frequency power H1 is large. The ratio of the high frequency power (H1 + H2) fed at the initial stage of the pulse to the steady state power (H1). (That is, (H1 + H2) / H1) is increased. Thereby, a desired plasma distribution is easily obtained.

  As described above, in the embodiment, when a plurality of power supplies to the electrodes are switched in a pulse manner, the high-frequency power is increased at the initial stage when the pulses are switched. That is, a plurality of high-frequency feeding points are provided on the electrode, and a pulse-modulated high frequency is fed to the feeding point. The first 5% to 20% of the pulse on time is 5% higher than the high-frequency power in the remaining period. The power is supplied more than 50%

  In this power supply method, when supplying high-frequency power to the plasma electrode from multiple locations in a pulsed manner, the initial high-frequency power of the pulse is increased from the rest of the period, so that plasma can be reliably formed, so the pulse repetition frequency is increased. In this case, a desired plasma distribution can be obtained, and a uniform plasma can be obtained even when a substrate having a large area is processed. That is, even when a substrate having a large area is processed by supplying high-frequency power in the VHF band, uniform plasma can be obtained.

  Here, assuming that the ratio ((H1 + H2) / H1) is the same between the small feeding point of the high-frequency power H1 in the steady state and the large feeding point, the plasma impedance at the initial stage of the pulse at the feeding point with the small high-frequency power H1. Therefore, it is difficult to form a desired electric field.

  On the other hand, in the embodiment, the ratio ((H1 + H2) / H1) at the small power supply point of the steady state high frequency power H1 is greater than the ratio ((H1 + H2) / H1) at the large power supply point in the steady state high frequency power H1. Therefore, the sensitivity to the influence of the dynamic change of the plasma impedance at the initial stage of the pulse can be equalized. This facilitates obtaining uniform plasma.

In the above embodiment, numerical values are shown for parameters such as gas flow rate, pressure, and high-frequency power, but these numerical values can be changed as appropriate. Further, although the case of a mixed gas of silane (SiH ₄ ) and hydrogen (H ₂ ) has been described as a film forming gas for forming a silicon thin film, a rare gas such as Ar or Ne may be further added. In addition, an appropriate gas type is selected according to the purpose of the process.

  In the plasma film forming apparatus according to the above embodiment, the configuration in which the film forming chamber 8 is formed by the vacuum chamber 1 and the electrode 5 is illustrated. However, the electrode 5 and the stage 2 are formed in the film forming chamber 8. The same effect can be obtained even if the power feeding method described in the above embodiment is applied to the configuration in which the above are arranged.

  Moreover, the plasma film-forming apparatus concerning said embodiment is applicable also to a plasma etching apparatus, an ashing apparatus, a sputtering apparatus etc., for example.

  In the above description, the horizontal film forming chamber 8 has been described. However, the plasma film forming apparatus according to the above embodiment can be applied to a vertical film forming chamber. Which type of film forming chamber is adopted can be appropriately selected according to the use of the plasma apparatus.

  As described above, the plasma film forming apparatus according to the present invention is useful for an apparatus for forming a thin film such as an amorphous silicon thin film or a microcrystalline silicon thin film on a substrate.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Stage 3 Exhaust port 4 Insulating flange 5 Electrode 5a 1st main surface 5b 2nd main surface 5b1, 5b2 Short side 6 Gas supply port 7 Shower plate 8 Deposition chamber 9 Deposition substrate 10a, 10b, 10c, 10d High-frequency power supply 21 Signal generator 22 Divider 23 Phaser 23a, 23b, 23c, 23d Phase adjustment unit 24a, 24b, 24c, 24d On / off switchers 25a, 25b, 25c, 25d High-frequency amplifiers 26a, 26b, 26c, 26d Matcher 27a, 27b, 27c, 27d Feed point 100 Plasma deposition system

Claims (3)

A deposition chamber is formed by the vacuum chamber and the first electrode, and a deposition target substrate is placed on the second electrode disposed opposite to the first electrode in the deposition chamber. A plasma film forming apparatus for forming a film using a plasma generated between one electrode and the second electrode,
The second main surface of the first electrode opposite to the first main surface facing the second electrode has a plurality of feeding points,
Each of the plurality of feeding points is fed with pulse-modulated high frequency power,
The pulse in the high frequency power has a first power in a first period in the on time, and has a second power in a second period following the first period in the on time,
The first power is rather high 5% or more than said second power,
The first period is a period of not less than the first 5% and not more than 20% in the on time,
The plasma deposition apparatus, wherein the second period is a remaining period of the on time . A deposition chamber is formed by the vacuum chamber and the first electrode, and a deposition target substrate is placed on the second electrode disposed opposite to the first electrode in the deposition chamber. A plasma film forming apparatus for forming a film using a plasma generated between one electrode and the second electrode,
The second main surface of the first electrode opposite to the first main surface facing the second electrode has a plurality of feeding points,
Each of the plurality of feeding points is fed with pulse-modulated high frequency power,
The pulse in the high frequency power has a first power in a first period in the on time, and has a second power in a second period following the first period in the on time,
The first power is rather high 5% or more than said second power,
The plurality of feeding points are:
A first feeding point;
A second feeding point to which a high-frequency power larger than the first feeding point is fed;
Have
The ratio of the first power to the second power at the first feeding point is greater than the ratio of the first power to the second power at the second feeding point.
A plasma film forming apparatus characterized by the above . A deposition chamber is formed by the vacuum chamber and the first electrode, and a deposition target substrate is placed on the second electrode disposed opposite to the first electrode in the deposition chamber. A plasma film forming method for forming a film using a plasma generated between one electrode and the second electrode,
The second main surface of the first electrode opposite to the first main surface facing the second electrode has a plurality of feeding points,
The plasma film forming method includes a power feeding step in which pulse-modulated high frequency power is fed to each of the plurality of power feeding points,
The power feeding step
A first step of feeding a first power to each of the plurality of feeding points;
Following the first step, a second step of feeding a second power to each of the plurality of feeding points;
Including
The first power is rather high 5% or more than said second power,
The first step is performed in the first 5% to 20% period of the pulse on time,
2. The plasma film forming method according to claim 1, wherein the second step is performed during the remaining period of the on time .