JP2021025118A - Semiconductor film deposition apparatus, film deposition method using the same and method for manufacturing semiconductor device using the film deposition method - Google Patents

Abstract

To provide a semiconductor film deposition apparatus capable of forming a high purity film, a film deposition method using the same, and a method for manufacturing a semiconductor device.SOLUTION: The semiconductor film deposition apparatus including a first shutter insertable on a substrate holding table achieves high vacuum in a chamber by an exhaust step of performing at least one of a first process of emitting nitrogen radicals into a chamber in the state of closing the first shutter and stopping and exhausting the nitrogen radicals and a process 2 of evaporating a getter material in the state of closing the first shutter once or more to deposit a semiconductor film on the substrate. Consequently, a high purity film is provided; a high purity semiconductor film can be formed; and an excellent semiconductor device can be obtained.SELECTED DRAWING: Figure 1

Description

The present invention relates to a semiconductor film forming apparatus, particularly a semiconductor film forming apparatus for forming a Group III nitride thin film, a film forming method thereof, and a method for manufacturing a semiconductor apparatus using the same.

In recent years, research on optical devices and electronic devices using GaN-based materials as wide bandgap semiconductor devices has been actively conducted. MOCVD and MBE are often used for crystal growth of such GaN-based materials. Recently, attention has been paid to film formation by the PLD method (Pulse Laser Deposition), which supplies group V by generating nitrogen radicals by plasma excitation while sublimating group III elements without heating with a short pulse laser.

The PLD method is a film forming method in which a target material is deposited on a substrate which is a film to be filmed by using a phenomenon called ablation in which the material is instantaneously evaporated by irradiating the target material with a short pulse laser. Unlike the MOCVD method, there is no need to supply organic source gas or ablation equipment. (Patent Document 1-4)

The MBE method is a film forming method in which a target is heated to a high temperature to deposit a film (for example, Patent Document 5), and an organic source gas is not used. However, since the entire apparatus of the MBE film forming apparatus becomes hot, a complicated mechanism for cooling the entire apparatus and controlling the temperature is required.
Compared with other film forming methods, the PLD method can form crystals of a GaN-based material with a film forming apparatus having a simple structure.

As the laser used in the PLD method, a laser having a pulse width (pulse length) of, for example, nanosecond order, picosecond order, or femtosecond order can be used.
If it is on the order of nanoseconds or more, it will be accompanied by heating of the target, but if the pulse width is on the order of picoseconds or femtoseconds, the target material of the laser-irradiated part will be used without heating the target. It can evaporate instantaneously. In particular, when the pulse width is on the order of picoseconds, stable film formation with a high deposition rate is possible.
In the present specification, for the sake of simplicity, the laser beam is simply referred to as a laser, and the film forming apparatus by the PLD method is simply referred to as a PLD film forming apparatus or a PLD apparatus.

Japanese Unexamined Patent Publication No. 2018-206867 JP-A-2018-170437 Japanese Unexamined Patent Publication No. 2017-157694 Japanese Unexamined Patent Publication No. 2007-288141 JP-A-2015-62255

The PLD film forming apparatus has a problem that moisture in the atmosphere in the vacuum chamber and hydrocarbon are easily taken into the GaN semiconductor layer during film formation. Oxygen supplied from water can be a donor in the semiconductor and can reduce the reproducibility of carrier concentrations. Further, it is known that carbon forms a complicated deep level in a GaN crystal if hydrocarbon or the like remains. It is important to reduce the impurities in the atmosphere in the vacuum chamber in this way in order to improve the quality of the GaN layer.

In view of the above problems, the present invention provides a semiconductor film forming apparatus, a film forming method thereof, and a method for manufacturing the semiconductor apparatus, which enable film formation in a state in which residual moisture, residual gas, etc. are effectively removed. With the goal.

The film forming method according to the present invention
Radical generator and
A chamber with a board holder and a target stage,
An exhaust device that exhausts the chamber and
In a semiconductor film forming apparatus provided with a first shutter that can be inserted and removed on a substrate holding table,
With the first shutter closed
A radical irradiation step of irradiating nitrogen radicals from the radical generator, and
The first process of executing the exhaust step of stopping the irradiation of nitrogen radicals from the radical generator and exhausting the gas in this order is included once or more.
With the first shutter open after the first process,
It is characterized by including a film forming step of evaporating a first target housed in a first target holder on the target stage and forming a film on a substrate held on the substrate holding table.

By adopting such a film forming method, it is possible to promote the exhaust of water or hydrocarbon, which has been difficult to exhaust in the past, by reacting with nitrogen radicals, and reduce the pressure of the ultimate vacuum. As a result, the purity of the film formed by the semiconductor film forming apparatus can be improved.

Further, the film forming method according to the present invention is
The radical generator includes a discharge chamber having a coil around it.
A catalyst is arranged in the discharge chamber.

Further, the film forming method according to the present invention is
The catalyst is characterized by being a C12A7 electride carrying Ru or Re.

Further, the film forming method according to the present invention is
In the radical irradiation step, the radical generator is characterized in that nitrogen radicals are generated from nitrogen gas to which at least one of 10% or less of oxygen, hydrogen, helium, neon, argon, krypton, and xenon is added.

By adopting such a film forming method, the effect of efficiently generating nitrogen radicals can be further enhanced.

Further, the film forming method according to the present invention is
The radical irradiation step is characterized in that the pressure is 10 [Pa] or less, and the product of the nitrogen radical density and the treatment time is 1 × 10 ¹² [cm ^-3 · min] or more.

By adopting such a film forming method, nitrogen radicals can effectively react with the remaining water and hydrocarbon in the chamber, and the partial pressure of these residual gases can be reduced.

Further, the film forming method according to the present invention is
At least before or after the first process
A second target made of getter material is housed in a second target holder on the target stage, and a second process of evaporating the second target is performed with the second shutter closed.

In such a film forming method, impurities remaining in the atmosphere of the chamber can be further removed by forming the evaporated getter material in the chamber, particularly in the first shutter.

Further, the film forming method according to the present invention is
The semiconductor film forming apparatus further includes a laser generator that irradiates the first target with a laser.
The laser emitted from the laser generator is characterized in that the pulse width is 1 picosecond or more and 1000 picoseconds or less.

In the semiconductor film forming apparatus having such a configuration, the target made of the getter material can be stably evaporated by setting the laser pulse width.

Further, the film forming method according to the present invention is
The first target is characterized by being composed of Group III elements.

By effectively discharging the residual water and hydrocarbon in the atmosphere in the chamber, a highly pure film, particularly a Group III element and its nitride can be obtained.

The method for manufacturing a semiconductor device according to the present invention is as follows.
It is characterized by including the above-mentioned film forming method.

Further, the method for manufacturing a semiconductor device according to the present invention is as follows.
The film forming step is characterized in that nitrogen radicals are irradiated from the radical generator.

By adopting such a method for manufacturing a semiconductor device, a high-purity film can be formed, in particular, a group III nitride semiconductor can be manufactured, and a semiconductor device such as a wide bandgap semiconductor device can be manufactured.

The semiconductor film forming apparatus according to the present invention is
A chamber with a board holder and a target stage,
An exhaust device that exhausts the chamber and
A first shutter that can be opened and closed with respect to the substrate holder,
A laser generator that irradiates the chamber with a pulsed laser,
The chamber is provided with a radical generator that irradiates nitrogen radicals.
The target stage comprises at least a first target holder for accommodating the deposited material and a second target holder for accommodating the getter material.
The target stage is characterized by including a target stage driving device that changes the positions of the first target holder and the second target holder.

Further, the semiconductor film forming apparatus according to the present invention is
The radical generator has a discharge chamber for generating plasma and a coil that winds around the discharge chamber.
A catalyst is arranged in the discharge chamber.

By adopting the semiconductor film forming apparatus having such a configuration, the pressure of the ultimate vacuum in the chamber can be significantly reduced. As a result, a highly pure film can be formed.

According to the present invention, it is possible to effectively remove residual water, residual gas, etc., which has been difficult in the past.
As a result, it becomes possible to provide a highly pure film, particularly a III-nitride semiconductor.
As an example, it was confirmed that the carbon and oxygen contents in the film were reduced by one or two orders of magnitude, respectively.

The main block diagram of the PLD apparatus which concerns on this invention. Top view showing the relationship between the target stage and the laser. The cross-sectional view which shows the structure of the radical generator. Sectional drawing of the catalyst installation part of a radical generator. The graph which shows the radical irradiation time dependence of a chamber pressure.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, none of the following embodiments give a limiting interpretation in finding the gist of the present invention. Further, the same or the same type of members may be designated by the same reference numerals and the description thereof may be omitted.

<PLD device>
FIG. 1 shows a configuration diagram of a PLD apparatus 1 which is a semiconductor film forming apparatus according to the first embodiment.
Inside the chamber (housing) 3 that is exhausted by the exhaust device 40 (vacuum pump) via the exhaust port (exhaust pipe port) 2 and can hold the inside in a vacuum, a target that can rotate around the rotating shaft 4 A stage 5 and a susceptor (substrate holding base) 7 for holding a substrate 6 (wafer) which is an object to be deposited (a film to be formed) are installed.
The susceptor 7 includes a heating heater 8, and the substrate 6 can be heated to, for example, 500 to 1000 [° C.].

A plurality of target holders 51 can be held in the target stage 5, and in this case, the target stage 5 can be rotated around the rotating shaft 4 by a target stage driving device using a stepping motor, a servomotor, or the like.
The target holder 51 generally houses a target made of a vapor-deposited material for depositing on the substrate 6, for example, Group III elements B, Ga, Al, In, but further remains in the chamber 3. It is configured to accommodate targets made of getter material having the property of gettering (capturing) substances (eg, oxygen, water), such as Ba, Ti, B and the like. Therefore, the target stage 5 includes a target holder 51 (first target holder) containing at least one vapor deposition material and a target holder 51 (second target holder) containing at least one getter material.
As will be described later, the position of the target holder 51, that is, the positions of the vapor deposition material and the getter material can be changed by rotating the target stage 5 around the rotation axis 4.
Ti can be used not only as a getter material but also as a vapor deposition material.

A viewport (laser introduction unit) 9 is provided in the chamber 3, and a laser radiated from the laser generator 10 via the viewport 9 can be introduced into the chamber 3.
An optical element such as a lens may be installed between the laser generator 10 and the viewport 9.

The optical axis of the laser introduced into the chamber 3 is adjusted to irradiate a specific position on the target stage 5. Therefore, the surface of the target housed in one of the plurality of target holders 51 can be irradiated.
FIG. 2 is a top view of an example of a target stage 5 provided with four target holders 51a, 51b, 51c, and 51d. For example, the target holder 51a holds a target made of a getter material, and the second, third, and fourth target holders 51b, 51c, and 51d hold a target made of a vapor-deposited material. As shown in FIG. 2, by rotating the target stage 5, a desired target holder 51 (for example, target holder 51a) is arranged at the irradiation position P of the laser L, and a target material to be evaporated by the laser is selected (changed). can do.

The pulse width of the laser emitted from the laser generator 10 is preferably set to 1 picosecond or more and 1000 picoseconds or less, so that the target material can be evaporated (plume generation) particularly stably. Specifically, for example, a wavelength of 1064 [nm], a pulse width of 10 to 20 [ps], a repetition frequency of 100 [kHz], and an average power of 5 [W]) are emitted, but the conditions are not limited to this.

Further, the PLD device 1 includes a first shutter (shielding plate) 11 between the target stage 5 (or the target holder 51) and the susceptor 7 (board 6).
The first shutter 11 is rotatably installed around the first opening / closing shaft 12.
The target stage 5 and the susceptor 7 are formed by rotating the first shutter 11 around the first opening / closing shaft 12 by a first shutter driving device (shutter opening / closing device) (not shown) using a stepping motor, a servomotor, or the like. It can be inserted (intervened) between and (closed state), and can be removed from the position between the target stage 5 and the susceptor 7 (open state). That is, the first shutter 11 is detachably (openable and closable) installed between the target stage 5 and the susceptor 7 by the first shutter driving device.

When the first shutter 11 is closed, the target material evaporated from the target is blocked by the first shutter 11 and does not reach the substrate 6, and is deposited on the first shutter 11.
When the first shutter 11 is opened, the target material is separated from the target holder 51 (target) and the susceptor 7 (board 6), and the target material evaporated from the target reaches the board 6 and can deposit the target material on the board 6. Will be.

The PLD device 1 includes a second shutter (shielding plate) 13 on the target stage 5, and the second shutter 13 is rotatably installed around the second opening / closing shaft 14. By rotating around the second opening / closing shaft 14 by a second shutter driving device (shutter opening / closing device) (not shown), the target stage 5 and the susceptor 7 (board 6) are detachably installed. There is.

The PLD device 1 includes a gas supply port 15 inside the chamber 3, and a radical generator (radical source) 16 is connected to the gas supply port 15.
For example, when forming a compound such as a nitride, the gas (for example, nitrogen) that reacts with the target material (deposited material) to form the compound is controlled to a predetermined flow rate and introduced into the surface of the substrate 6. The reactive gas reacts with the vaporized material evaporated from the target, and a compound (for example, a Group III nitride such as GaN) is deposited on the surface of the substrate 6.
By converting the reactive gas into active radicals by the radical generator 16, the reaction with the vapor-deposited material is promoted, and the compound can be stably obtained.
The radical generator 16 is a device that applies high-frequency power to a coiled electrode to generate plasma and emit radicals, as disclosed in Document 5 for an embodiment applied to an MBE device, for example. It may be used when forming a group III nitride as in.

A third shutter (shielding plate) 18 is installed at the gas discharge port of the radical generator 16. The third shutter 18 is rotatably installed around the third opening / closing shaft 19.
By rotating the third shutter 18 around the third opening / closing shaft 19 by a third shutter driving device (shutter opening / closing device) (not shown), the third shutter 18 is placed between the radical generator 16 and the susceptor 7 (board 6). It is installed so that it can be inserted and removed. By inserting and removing the third shutter 18, it is possible to supply and stop radicals to the susceptor 7 (substrate 6).

The PLD device 1 is provided with a leak port 20 capable of introducing the atmosphere, and the chamber 3 can be opened to the atmosphere in order to perform maintenance work such as replacement of a target and periodic cleaning of the PLD device 1. ..
In this case, it goes without saying that the valve of the exhaust port 2 leading to the vacuum pump is closed.

The first shutter 11, the second shutter 13, and the third shutter 18 move by rotating around the first opening / closing shaft 12, the second opening / closing shaft 14, and the third opening / closing shaft 19, respectively. Although an example is shown, it may be translated and moved in parallel.
Further, the shapes of the first shutter 11, the second shutter 13, and the third shutter 18 may be a disk shape, a rectangular shape, or another shape.

<Radical generator>
FIG. 3 is a cross-sectional view showing a main configuration of the radical generator 16.
A gas whose flow rate is controlled by the mass flow controller 17, for example, nitrogen, is introduced from the gas introduction port 21 and supplied to the discharge chamber 23 made of PBN (pyrolytic boron nitride) or quartz via the supply pipe 22.
The high frequency (alternating current) power (for example, 13.56 [MHz]) generated by the high frequency power supply 24 (RF power supply) is impedance-matched by the matching box 25 and supplied to the coil 27 via the transmission line 26. The coil 27 is wound around the discharge chamber 23 and excites the gas in the discharge chamber 23 to generate radicals.
One of the transmission lines 26 is connected to the ground.

The generated radicals are discharged from the opening 30 provided in the housing 29 via the orifice 28 (first orifice) provided at the tip of the discharge chamber 23.
Further, although the orifice 28 is composed of one hole in the figure, a plurality of holes may be arranged in an array.
Further, the distribution of the emitted radicals may be controlled by the shape of the orifice 28. For example, the orifice 28 (opening portion) has a cylindrical shape and its radius and height (length) can be adjusted, or a truncated cone shape can be formed and the radius and height of its bottom surface and top surface can be adjusted.
A plurality of types of orifices 28 can be prepared and appropriately changed according to the vapor deposition material and the film formation conditions. For example, a second orifice 33 is further provided in a part of the shutter 18 installed in front of the opening 30 shown in FIG. 3, and the shutter 18 is rotated to stop the emission of radicals or a second. Radicals may be emitted from the orifice 33 of the.
In this case, as the second orifice 33, the shutter 18 is provided with a second orifice 33 having a plurality of types of shapes, and the shutter 18 can be rotated to appropriately select the second orifice 33.

The coil 27 is composed of a hollow pipe, and cooling water can flow through the coil 27. The cooling water is supplied and discharged from the water supply / drainage port 31. The water supply / drainage port 31 is provided in the matching unit 25, but is not limited thereto.

The catalyst 32 may be provided in the discharge chamber 23. FIG. 3 shows an example provided between the portion wound by the coil 27 and the orifice 28. FIG. 4 shows an enlarged cross-sectional view of the discharge chamber 23 and the catalyst 32.
The catalyst 32 can be provided along the inner wall of the discharge chamber 23 as shown in FIG. 4A, but may have a mesh-like disk shape as shown in FIG. 4B. , As shown in FIG. 4 (c), the particles may be granulated and filled at intervals that allow gas to pass through.
The catalyst 32 can utilize the catalytic action of the metal surface and promotes the dissociation of nitrogen molecules adsorbed on the metal surface. That is, the catalytic action of the metal surface can weaken the bond of nitrogen molecules, promote the generation of active nitrogen radicals, and increase the density of nitrogen radicals.
In addition to the metal, a metal nitride such as WN (tungsten nitride) or TiN (titanium nitride) also has a catalytic action, and the metal or the metal nitride can be used as the catalyst 32.

Further, as the catalyst 32, a catalyst in which metal nanoparticles (fine particles on the order of nanometers) are supported on a carrier (for example, a porous substance such as zeolite) can be used, but Ru nanos are preferably used as the metal. C12A7 electride which was supported particles (12CaO · _7Al 2 _{O 3)} can be used. In addition to Ru, Re may be used. In particular, C12A7 electride has high conductivity, is excellent in the function of donating electrons to the supported metal fine particles, promotes the catalytic properties of the metal fine particles, and is a very stable material. Therefore, in such a discharge chamber 23, Even if it is installed in, it is highly durable and suitable.
The catalyst 32 may be installed in the discharge chamber 23 at a location around which the coil 27 is wound. The electromagnetic induction raises the temperature of the metal fine particles of the catalyst 32 and promotes nitrogen decomposition. Further, the catalyst 32 may be grounded, but it is not always necessary to ground the catalyst 32 because electrons can be supplied by the generated plasma.

<Processing method of film forming equipment>
Hereinafter, a method of exhausting the chamber 3 (making a high vacuum) in order to form a film using the PLD device 1 will be described.
If water or hydrocarbon remains in the atmosphere inside the chamber 3 due to water or hydrocarbon adhering to the inner wall of the chamber 3 of the PLD device 1, it is difficult to discharge the water or hydrocarbon. Water and hydrocarbon remaining in the atmosphere may be incorporated as impurities into the film deposited on the substrate 6 and reduce the purity (quality) of the deposited film.

In the exhaust and film forming method according to the present invention, water and hydrocarbon, which are particularly difficult to discharge, can be effectively discharged by using nitrogen radical irradiation. As a result, it is possible to significantly reduce the base pressure (reaching vacuum pressure) and improve the quality of the film formed by the PLD method.
In each process described below, the chamber 3 is exhausted by a vacuum pump (for example, a turbo pump) via the exhaust port 2.

First, the substrate 6 which is the object of film formation is placed on the susceptor 7. Then, before the vapor-deposited material is deposited on the substrate 6 by laser irradiation, the following process is executed as an exhaust treatment (process) for bringing the chamber 3 into a high vacuum state.
When the chamber 3 is opened to the atmosphere in the process of placing the substrate 6 on the susceptor 7, the chamber 3 is exhausted by using only the exhaust device 40 as usual. The following processes 1 and 2 are performed after the conventional exhaust process using only the exhaust device 40. For example, only the exhaust device 40 is used and executed after reaching a predetermined pressure. The predetermined pressure may be a preset pressure value, or may be a pressure when the pressure drop is saturated.

Process 1 (first process):
The first shutter 11 and the second shutter 13 are closed, the third shutter 18 is opened, and nitrogen radicals are radiated into the chamber 3 from the radical generator 16 while being exhausted by the exhaust device 40. For the sake of simplicity, this process is referred to as a radical irradiation step.
In this case, the laser is not emitted from the laser generator 10.

In order to generate nitrogen radicals, nitrogen gas whose flow rate is controlled by the mass flow controller 17 is supplied to the radical generator 16. At this time, a small amount of additives, specifically 10% or less of oxygen and hydrogen, and one or more gases selected from rare gases such as helium, neon, argon, neon, krypton, and xenon are added to the nitrogen gas. It may be mixed.
By adding such a gas to the nitrogen gas, the generation of plasma is promoted and the density of nitrogen radicals can be improved.
In particular, when hydrogen is added to nitrogen gas to generate nitrogen radicals, if a catalyst 32 in which metal fine particles are supported on C12A7 electride is used, the added hydrogen is captured by the C12A7 electride on the surface of the metal fine particles. , Prevents hydrogen from inhibiting the divergence of nitrogen.

Specifically (but not limited to), the nitrogen radical treatment is carried out under the condition that the pressure of the chamber 3 is 10 [Pa] or less, and the nitrogen radical density is 1 × 10 ¹² [cm ^-3 ] or more. The treatment is carried out under the condition that the treatment time is 1 minute or more, or the product of the nitrogen radical density and the treatment time is 1 × 10 ¹² [cm ^{-3 · min] or more.} At this time, heating of the PLD apparatus 1 is not particularly necessary, but the susceptor 7 holding the substrate 6 may be heated by the heater 8 in preparation for the subsequent film formation.
The pressure in the chamber 3 can be controlled by adjusting the valve opening degree provided in the exhaust port 2 and controlling the flow rate of nitrogen gas by the mass flow controller 17.

It was confirmed by a quadrupole mass analyzer (QMASS) that the partial pressure of water could be reduced when the nitrogen radical was irradiated as compared with the case where the nitrogen radical was not irradiated.
The reason why the partial pressure of water could be reduced is considered to be the following reaction formula.
H ₂ O + N ^* → NH ₃ + NO + H ₂ (Equation 1)
That is, the remaining water is effectively discharged by being converted into a substance having a high vapor pressure and a low boiling point, so that the partial pressure of water can be reduced.
Further, as shown below, for example, hydrocarbon can be effectively discharged by being converted into a substance that can be easily exhausted by nitrogen radicals.
CxOyHz + N ^* → CO + NH + NO (Equation 2)
As a result, water and hydrocarbon are discharged, the base pressure is reduced, and a higher vacuum is realized.

The result of confirming the effect of this process is shown in FIG.
Black circles (●) in the figure indicate cases where nitrogen gas (N2) having a flow rate of 20 [sccm] ([ml / min (standard state)]) is introduced into the radical generator 16 and the nitrogen radicals are irradiated into the chamber 3. Shows pressure change. The solid line shows the pressure when nitrogen gas (N2) having a flow rate of 20 [sccm] is introduced into the chamber 3 without generating nitrogen radicals.

As shown by the black circles in the figure, when nitrogen radicals are irradiated into the chamber 3, the nitrogen radicals react with water and hydrocarbon in the chamber 3 (including the inner wall of the chamber 3) to generate degassing, so compare with the solid line. Then, the pressure rises once. However, the pressure tends to decrease with the nitrogen radical irradiation time. It can be understood that after the irradiation time of the nitrogen radical is about 50 minutes or later, the pressure becomes a constant value and becomes lower than the solid line.
That is, when the nitrogen radical is not irradiated, the water and the hydrocarbon in the chamber 3 remain, but when the nitrogen radical is irradiated, the water and the hydrocarbon in the chamber 3 are removed by the nitrogen radical. Therefore, in the end, the pressure in the chamber 3 can be reduced by the pressure corresponding to the partial pressure contributed by water or hydrocarbon.

After that, the nitrogen radical irradiation is stopped. The inside of the chamber 3 is exhausted by the exhaust device 40 via the exhaust port 2 to reduce the pressure. By removing water and hydrocarbon adhering to the atmosphere in the chamber 3 or the inner wall of the chamber 3, the pressure of the ultimate vacuum is further reduced in this exhaust step.

If the correlation data between the pressure at the time of nitrogen radical irradiation and the ultimate vacuum pressure is acquired in advance, the desired ultimate vacuum pressure can be realized by monitoring the pressure in the nitrogen radical irradiation step.

Although the exhaust device 40 is used for exhaust during the radical irradiation step, the state in which the supply of nitrogen radicals is stopped is referred to as an exhaust step for the sake of simplicity, and the radical irradiation step and the exhaust step are described in this order. The process to be executed is called process 1.
This process 1 may be repeated at least once or multiple times until the desired ultimate vacuum is obtained.

Process 2 (second process):
The rotation angle of the target stage 5 is adjusted so that the target holder 51 that houses the getter material as a target is irradiated with the laser.
The first shutter 11 is closed, the second shutter 13 is opened, and the target made of getter material (for example, Ti, B, Ba) is irradiated with a laser from the laser generator 10.
In this case, the radical irradiation from the radical generator 16 is not performed.

The getter material evaporates from the area irradiated with the laser. The evaporated getter material is mainly deposited (deposited) on the first shutter 11, but not on the substrate 6.
A part of the getter material may be deposited on the inner wall of the chamber 3 other than the first shutter 11.

The surface of the getter material deposited on the first shutter 11 or the like is active and captures (gettering) reactive gases such as water, oxygen, and nitrogen.
When the getter material was evacuated only by the vacuum pump without evaporating, the base pressure was ^10-6 [Pa], but it was evaporated by the PLD method using B (boron) as the getter material and the first shutter 11 When it was deposited on the ground, the base pressure became ^10-8 [Pa], and a double-digit pressure drop (improvement) could be confirmed.
This double-digit pressure drop is due to the getter material capturing water, hydrocarbon, and other active residual gases in the chamber 3.
The first shutter 11 prevents the formation of the getter material on the substrate 6 and acts as a getter surface. Further, even when the first shutter 11 is open, since the first shutter 11 exists in the vicinity of the substrate 6, there is an effect of enhancing the gettering effect in the vicinity of the substrate 6 to be formed.

In this process 2, the third shutter 18 may be closed. Since most getter materials are deposited on the first shutter 11 and the inner wall of the chamber 3 around it, there is little adhesion to the radical generator 16, so it is not essential to close the third shutter 18. However, by closing the third shutter 18, the getter material is unnecessarily deposited on the radical generator 16, the nitrogen radicals irradiated from the radical generator 16 are captured, and the nitrogen radicals supplied into the chamber 3 are released. The risk of reduction can be prevented.

Needless to say, in the above processes 1 and 2, the chamber 3 is exhausted by the exhaust device 40 via the exhaust port 2.

By the above processes 1 and 2, water and hydrocarbon in the atmosphere of the chamber 3 can be effectively removed (or the partial pressures of each can be reduced).

By reducing the partial pressure of carbon and oxygen in the atmosphere at the time of film formation, the concentration of carbon and oxygen incorporated into the film-forming GaN can be reduced. The concentrations of carbon and oxygen in the membrane were compared and investigated by SIMS analysis for the samples with and without nitrogen radical treatment. As a result, in the sample without nitrogen radical treatment, the carbon (C) concentration was 3 × 10 ¹⁹ [cm ^-3 ] and the oxygen (O) concentration was 4 × 10 ²⁰ [cm ^-3 ], whereas the nitrogen radical was In the treated sample, the carbon (C) concentration was 2 × 10 ¹⁸ [cm ^-3 ], the oxygen (O) concentration was 2 × 10 ¹⁸ [cm ^-3 ], the carbon concentration was reduced by an order of magnitude, and the oxygen concentration was reduced. Has decreased by two orders of magnitude, confirming that the purity of the film is significantly improved.

The order of these two processes is not limited, but when the processes 1 and 2 are executed in this order, the by-products generated by reacting with the nitrogen radicals in the process 1 can be more effectively eliminated in the process 2. ..

In the film forming process, when the deposited film is nitrided, for example, when GaN is formed, the process 2 and the process 1 can be preferably executed in this order. The atmosphere inside the chamber 3 can be prefilled with nitrogen radicals.
If the process 1 is executed after the process 2, the active nitrogen radicals are captured by the getter material deposited on the first shutter 11 or the like immediately after the nitrogen radical irradiation, so that the nitrogen radical irradiation time is lengthened. Time adjustment may be required.
In addition, only one of process 1 and process 2 may be executed.

After that, the first shutter 11 and the second shutter 13 are opened, and the film forming process is executed by the PLD method.
For example, by irradiating a pulsed laser on Ga (but not limited to) the Group III element, opening the third shutter 18, and irradiating nitrogen radicals from the radical generator 16, Group III nitride is used. A substance (Ga nitride) can be formed.
Since impurities in the internal atmosphere of the chamber 3 are reduced, high-purity Ga nitride can be formed. By using the obtained semiconductor which is a group III nitride, it becomes possible to provide a wide bandgap semiconductor device having good characteristics.
In addition to the nitrides of Group III elements, high-purity film formation of other metal nitrides (WN, TiN, etc.) is also possible.
Needless to say, a high-purity metal or semiconductor other than nitride can be formed by forming a film by the PLD method without irradiating with nitrogen radicals.
Furthermore, it goes without saying that other compounds (or compound semiconductors) can be formed by irradiating radicals of elements other than nitrogen (for example, oxygen).

In the film forming method of the PLD device 1, the combined flow of the process 1 and / or the process 2 and the film forming is registered in advance in the memory of the PLD device 1, and the PLD device 1 is controlled by the arithmetic processing unit. Can be processed automatically with.

Specifically, the process 1 can be exhausted according to the following flow.
(1) The first pressure is registered in the memory as a determination value in advance, the above process 1 is executed, and then the pressure in the chamber 3 is measured.
(2) If the pressure in the chamber 3 is equal to or lower than the first pressure, the next step, for example, a film forming process or process 2 is executed.
(3) If the pressure in the chamber 3 is higher than the first pressure, the process 1 is executed again.
(4) If the pressure in the chamber 3 does not become equal to or lower than the first pressure even after the process 1 is executed a predetermined number of times (for example, 5 times), the PLD device 1 displays an error message.

Similarly, the process 2 can be exhausted according to the following flow.
(1) A second pressure is registered in the memory as a determination value in advance, the process of process 2 is executed, and then the pressure in the chamber 3 is measured.
(2) If the pressure in the chamber 3 is equal to or lower than the second pressure, the next step, for example, a film forming process or process 1 is executed.
(3) If the pressure in the chamber 3 is higher than the second pressure, the process 2 is executed again.
(4) If the pressure in the chamber 3 does not fall below the second pressure even after the process 2 is executed a predetermined number of times (for example, 5 times), the PLD device 1 displays an error message.

For example, when the process 2 is executed after the process 1, the first pressure may be set higher than the second pressure. On the contrary, when the process 1 is executed after the process 2, the second pressure may be set higher than the first pressure.

In the case of the film forming process, the laser is irradiated to the target made of the vapor-deposited material housed in the target holder 51 by the PLD method to perform the film forming process, but when forming a nitride, the target material is evaporated by the laser. However, nitrogen radicals may be irradiated.

The above film forming method is particularly effective in the semiconductor film forming apparatus by the PLD method, in which it has been difficult to improve the ultimate vacuum (reduction of pressure) in the past, but it can also be applied to the semiconductor film forming apparatus by the MBE method. is there.
That is, in the MBE device, instead of evaporating the target material and the gettering material by laser irradiation, a known heating device such as a heater or an electron beam is provided, and the target material and the gettering material housed in the target holder (crucible) are placed. It may be heated and evaporated, and a radical generator 16 may be installed in the MBE device so that radicals can be introduced into the chamber of the MBE device.
In this case, process 1 or process 2 or a combination of process 1 and process 2 may be executed before the film formation on the substrate 6 (deposition of the target material) by the MBE method. This makes it possible to further improve the ultimate vacuum (reduce the pressure) even in the MBE device.

According to the present invention, it is possible to further improve the ultimate vacuum (low pressure) in the semiconductor film forming apparatus, and as a result, it is possible to provide a film containing high-purity III nitride.
Further, the obtained high-purity III nitride can be expected to be applied to products using various semiconductor devices such as power devices and light emitting devices, and has high industrial applicability.

1 PLD device 2 Exhaust port (exhaust piping)
3 chamber (housing)
4 Rotating shaft 5 Target stages 51, 51a, 51b, 51c, 51d Target holder 6 Board 7 Suceptor (board holding base)
8 Heater 9 Viewport (laser introduction)
10 Laser generator 11 First shutter (shielding plate)
12 First opening / closing shaft 13 Second shutter (shielding plate)
14 Second opening / closing shaft 15 Gas supply port 16 Radical generator 17 Mass flow controller 18 Third shutter (shielding plate)
19 Third on-off shaft 20 Leak port 21 Gas inlet 22 Supply pipe 23 Discharge chamber 24 High-frequency power supply 25 Matcher 26 Transmission line 27 Coil 28 Orifice (first orifice)
29 Housing 30 Opening 31 Water supply / drainage port 32 Catalyst 33 Second orifice 40 Exhaust device (vacuum pump)

Claims (12)

Radical generator and
A chamber with a board holder and a target stage,
An exhaust device that exhausts the chamber and
In a semiconductor film forming apparatus provided with a first shutter that can be inserted and removed on a substrate holding table,
With the first shutter closed
A radical irradiation step of irradiating nitrogen radicals from the radical generator, and
The first process of executing the exhaust step of stopping the irradiation of nitrogen radicals from the radical generator and exhausting the gas in this order is included once or more.
With the first shutter open after the first process,
A film forming method comprising a film forming step of evaporating a first target housed in a first target holder on the target stage and forming a film on a substrate held by the substrate holding table. The radical generator includes a discharge chamber having a coil around it.
The film forming method according to claim 1, wherein a catalyst is arranged in the discharge chamber. The film forming method according to claim 1 or 2, wherein the catalyst is a C12A7 electride carrying Ru or Re. In the radical irradiation step, the radical generator is characterized in that nitrogen radicals are generated from nitrogen gas to which at least one of 10% or less of oxygen, hydrogen, helium, neon, argon, krypton, and xenon is added. Item 3. The film forming method according to any one of Items 1 to 3. The radical irradiation step is any of claims 1 to 4, wherein the pressure is 10 [Pa] or less, and the product of the nitrogen radical density and the treatment time is 1 × 10 ¹² [cm ^{-3 · min] or more.} The film forming method according to item 1. At least before or after the first process
A second process of accommodating a second target made of getter material in a second target holder on the target stage and evaporating the second target with the second shutter closed is performed. The film forming method according to any one of claims 1 to 5, wherein the film forming method is characterized. The semiconductor film forming apparatus further includes a laser generator that irradiates the first target with a laser.
The film forming method according to any one of claims 1 to 6, wherein the laser irradiated from the laser generator has a pulse width of 1 picosecond or more and 1000 picoseconds or less. The film forming method according to any one of claims 1 to 7, wherein the first target is composed of a group III element. A method for manufacturing a semiconductor device, which comprises the film forming method according to any one of claims 1 to 8. The method for manufacturing a semiconductor device, which comprises irradiating a nitrogen radical from the radical generator in the film forming step according to claim 8. A chamber with a board holder and a target stage,
An exhaust device that exhausts the chamber and
A first shutter that can be opened and closed with respect to the substrate holder,
A laser generator that irradiates the chamber with a pulsed laser,
The chamber is provided with a radical generator that irradiates nitrogen radicals.
The target stage comprises at least a first target holder for accommodating the deposited material and a second target holder for accommodating the getter material.
The target stage is a semiconductor film forming apparatus including a target stage driving device that changes the positions of the first target holder and the second target holder. The radical generator has a discharge chamber for generating plasma and a coil that winds around the discharge chamber.
The semiconductor film forming apparatus according to claim 11, wherein a catalyst is arranged in the discharge chamber.

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