JP2013221176A - Method and apparatus for manufacturing thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deposit a film without increasing a substrate temperature even when deposition is performed through several deposition steps.SOLUTION: By performing a first deposition in a state where a conveyance tray 601 is set to a ground potential, an annealing temperature for improving a lifetime is secured and the conveyance tray 601 is insulated from a facility ground, and by performing a second deposition at a discharge power higher than that in the first deposition, a desired film thickness can be achieved without increasing a substrate temperature too much. This can reduce standby time for the deposition and prevent delamination of a film even when the deposition is performed through several deposition steps.

Description

  The present invention relates to a thin film manufacturing method and a thin film manufacturing apparatus for forming a film on a substrate by sputtering.

  A thin film manufacturing method using a vacuum process is used in various fields such as semiconductors, solar cells, television displays, and optical elements. Thin film manufacturing methods include electron beam evaporation, thermal evaporation, CVD, and sputtering. Among these, the sputtering method is widely used because of its simplicity and high film formation speed.

  The sputtering method is an excellent technique in that an insulating material such as a dielectric or a nitride film can be formed at a high speed and a low temperature, and has been put into practical use in the production of a surface protective film of a semiconductor device.

  Sputtering apparatuses used for the sputtering method are classified into several film formation methods depending on the method of transporting the substrate in the facing portion of the target fixed to the apparatus housing. For example, in a facing part of the target, a passing method in which the substrate placed on the transfer tray is moved in one direction, a rotating method in which the substrate is rotated in front of the target, and a single wafer on which only one substrate is installed in front of the target to perform sputtering There are expressions.

  When a large substrate such as a 2 m square glass substrate is formed, or when a small substrate is collectively formed, a film formation process is generally performed by a passing method with excellent production tact. For example, as the collective film, there are cases where about 100 solar cell substrates of 150 mm square are collectively formed.

  In order to deposit a film with a predetermined film thickness using a passing-type sputtering apparatus, it is necessary to determine film forming conditions for sputtering. Main film forming conditions in the case of the passing method include discharge output, substrate transfer speed, film forming pressure, and the like. In the pass-type film formation, when the discharge power during sputtering is constant, the film formation rate tends to be inversely proportional to the tray transfer speed. Therefore, by adjusting the tray transfer speed during film formation, The film thickness can be easily controlled in consideration of substrate damage.

  In addition, the potential relationship between the transport tray for transporting the substrate to be deposited and the equipment ground is also an important deposition condition. For example, when the transport tray and the equipment ground are connected and have the same potential, the thermoelectrons generated during the sputtering tend to collide with the transport tray, and the temperature of the substrate placed on the transport tray tends to increase. On the other hand, when the transfer tray and the equipment ground are insulated, the thermoelectrons hardly collide with the transfer tray, so that the temperature of the substrate placed on the transfer tray is unlikely to rise.

  In order to ensure a certain level of the characteristics of the electronic device, management of the film thickness during film formation is one of the important factors. Therefore, in order to obtain a desired film thickness, there has been proposed a method of forming a film by determining the film formation conditions of the next substrate while managing the film thickness at the time of film formation (see, for example, Patent Document 1). .

  FIG. 8 is a conceptual diagram for explaining a conventional thin film manufacturing method, and is a diagram showing an apparatus configuration used in the conventional thin film manufacturing described in Patent Document 1. In the conventional thin film manufacturing method, the film formation process is performed a plurality of times on the substrate 5 in the first vacuum vessel 1. In this thin film manufacturing method, the film thickness of the substrate 5 after the nth film formation and the n + 1th film formation are performed in the second vacuum container 7 provided in the same film forming apparatus every time the film formation process is performed. The film thickness of the substrate 5 is measured by the film thickness measuring means 9. Then, from these results, the n + 2th film formation condition is adjusted, and the n + 2th film formation is performed based on the adjusted film formation condition.

Japanese Patent Laid-Open No. 10-088348

  However, in the conventional method for forming a nitride film by the thin film manufacturing method, it is necessary to form the nitride film in a plurality of times in order to suppress the temperature rise of the substrate 5. Therefore, a thin film other than the nitride film is formed at the interface between the nitride films between the film formation process, and there is a problem in that peeling occurs in the nitride film depending on conditions.

  In addition, when the film is formed in a plurality of times, if a sufficient substrate cooling time is provided for each film formation so that the substrate temperature does not increase, the surface quality of each layer is different from that of a nitride film such as a surface oxide film. This layer may be formed, and depending on the conditions, there is a problem that peeling at the interface occurs.

  In order to solve the above-described problems, the thin film manufacturing method and the thin film manufacturing apparatus of the present invention aim to form a predetermined film thickness without excessively raising the temperature.

  In order to achieve the above object, a thin film manufacturing method of the present invention is a thin film manufacturing method in which a substrate mounted on a transport tray is passed a plurality of times at a position facing a target, and a film is formed on the substrate by sputtering. A first film forming step of forming a film on the substrate with a first discharge power in a state where the transfer tray is connected to the equipment ground; and a state where the transfer tray is insulated from the equipment ground. And a second film formation step of forming a film on the film formed in the first film formation step with a second discharge power having a power higher than that of the first discharge power.

  In order to achieve the above object, the thin film manufacturing apparatus of the present invention is a thin film manufacturing apparatus that forms a film on a substrate by sputtering a plurality of times, and is provided at a position facing the target and the target. It has a rail, a transport tray that reciprocates on the rail in a state where the substrate is placed, and a tray-carrier conduction toggle that connects or insulates the transport tray with equipment ground.

  As described above, the thin film manufacturing method and thin film manufacturing apparatus of the present invention can form a film with a desired film thickness without excessively raising the temperature.

The conceptual diagram which shows the structure of the thin film manufacturing apparatus in embodiment of this invention Flowchart for explaining a thin film manufacturing method in an embodiment of the present invention The conceptual diagram explaining the structure of the thin film manufacturing apparatus with which a tray-carrier conduction toggle is a connection state The conceptual diagram explaining the structure of the thin film manufacturing apparatus whose tray-carrier conduction | electrical_connection toggle is an insulation state The figure which illustrates the lamination | stacking state of the thin film at the time of forming into a film 4 times in embodiment of this invention The figure showing the relationship between the discharge electric power in the embodiment of this invention, and the temperature at the time of film-forming The figure showing the relationship between the discharge electric power in the embodiment of this invention, the temperature at the time of film-forming, and the change of a lifetime ratio Conceptual diagram explaining a conventional thin film manufacturing method

Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the following description, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
First, a thin film manufacturing apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram showing a configuration of a thin film manufacturing apparatus according to an embodiment of the present invention.

  As an example of the thin film manufactured in the embodiment of the present invention, there is a thin film formed on a solar cell substrate. As a thin film formed on the solar cell substrate, for example, there is a nitride film which is formed on a substrate on which amorphous silicon is formed and has a role of a surface protective layer and an antireflection layer of about 80 to 100 nm. A solar cell substrate is an example of a device that can improve device characteristics by performing annealing while raising the substrate temperature to some extent during sputtering. In addition, it is generally known that when amorphous silicon is annealed at about 150 to 250 ° C., the lifetime that contributes to the solar cell characteristics is recovered.

  In the thin film manufacturing apparatus of this embodiment, when forming a nitride film, as shown in FIG. 1, the transport tray 601 and the equipment ground are set to the same potential, and the substrate temperature is increased by thermionic electrons. The substrate 701 placed on the transfer tray 601 is formed while being annealed.

  An example of the thin film manufacturing apparatus of the present embodiment is a passing type sputtering apparatus as shown in FIG. In a pass-through sputtering apparatus, if all the films are formed in one pass, the temperature of the substrate may be excessively increased due to the collision of thermoelectrons. Therefore, in this embodiment, a thin film having a predetermined thickness is formed by performing film formation in a plurality of times while increasing the substrate conveyance speed to avoid an increase in the temperature of the substrate.

  Here, in the thin film manufacturing apparatus according to this embodiment, a nitride film having a standard thickness of 80 to 100 nm as a solar cell is formed on a 150 mm square silicon substrate 701 on which amorphous silicon is formed by sputtering. Will be described as an example.

  As shown in FIG. 1, in the thin film manufacturing apparatus according to the present embodiment, an electrode 1001 to which a target 301 is fixed is fixed in a vacuum chamber 201 for film formation. A film forming side transfer rail 411 is provided so as to be movable. A carrier tray 601 and a substrate 701 placed on the carrier tray 601 are placed on the carrier carrier 1201. By moving the transfer carrier 1201 on the substrate loading side transfer rail 401 or the film formation side transfer rail 411, the substrate 701 is moved relative to the target 301 by moving back in the Z direction shown in FIG. The transfer carrier 1201 is in contact with the film formation side transfer rail 411 and has the same potential as the equipment ground. Although not shown, the film forming vacuum chamber 201 is provided with a vacuum exhaust unit and a gas introducing unit so that the pressure and the degree of vacuum in the film forming vacuum chamber 201 can be adjusted. The target 301 is, for example, a silicon target.

  The substrate loading / unloading vacuum chamber 101 is provided with a loading / unloading gate valve 551. The substrate 701 and the transport tray 601 are set on the transporting carrier 1201 through the loading / unloading gate valve 551, and the transporting carrier 1201 is loaded into the substrate. It is the structure put on the side conveyance rail 401. FIG. Although not shown, the substrate loading / unloading chamber 101 is provided with a vacuum exhaust means.

  A gate valve 501 is connected between the substrate loading / unloading vacuum chamber 101 and the film forming vacuum chamber 201. A carrier carrier 1201 on which the substrate 701 and the carrier tray 601 placed in the substrate loading / unloading vacuum chamber 101 are placed is placed on the substrate loading side transportation rail 401 and is transported to the film forming vacuum chamber 201. When the gate valve 501 is opened, the transfer carrier 1201 on which the substrate 701 and the transfer tray 601 are placed can be transferred from the substrate loading side transfer rail 401 to the film formation side transfer rail 411.

  When the transport carrier 1201 is transported on the film-forming-side transport rail 411 and reaches the end in the “bound” direction shown in FIG. 1, the tray-carrier conduction toggle 1301 comes into contact with the toggle switching shaft 1401, and the tray -The carrier conduction toggle 1301 is inclined to the non-connection side, and the transport tray 601 is insulated from the equipment ground.

  Further, although the substrate loading side transfer rail 401 and the film forming side transfer rail 411 are not shown, the electric motors connected to the respective rails are rotated in the normal direction or the reverse direction, thereby being illustrated in FIG. It is possible to move the transport carrier 1201 in the direction of “go / return”.

  In FIG. 1, a DC voltage, an AC voltage, or a high-frequency voltage is supplied from the power source 1101 to the electrode 1001. When a predetermined discharge power value is set in the arithmetic device 901, the discharge power is set in the power source 1101, and film formation is performed with the predetermined power. Since a plurality of discharge powers corresponding to the position and traveling direction of the carrier carrier 1201 can be set in the arithmetic device 901 as discharge recipes, the discharge power can be switched between the going direction and the returning direction in FIG.

  The transport carrier 1201 and the transport tray 601 are connected by a tray-carrier conduction toggle 1301 provided on the transport tray 601. When the tray-carrier conduction toggle 1301 is tilted to the connection side, the transport carrier 1201 and the transport tray 601 have the same potential, and the transport tray 601 has the same potential as the equipment ground via the transport carrier 1201. On the other hand, when the tray-carrier conduction toggle 1301 is tilted to the insulation side, the transport carrier 1201 and the transport tray 601 are insulated, and the transport tray 601 is insulated from the equipment ground via the transport carrier 1201. Toggle switching shafts 1401 are provided at both ends of the film-forming vacuum chamber 201 on the outgoing side and the return side, respectively.

  The thin film manufacturing apparatus according to the present embodiment has a configuration in which the tray-carrier conduction toggle 1301 is switched when the transport carrier 1201 reaches both ends. With this configuration, the potential between the transfer tray 601 and the equipment ground can be switched from the connected state (the same potential) to insulation in a vacuum state in the chamber. In addition, it is set as the structure which does not provide the toggle switching shaft 1401 of a return side edge part, and when connecting the conveyance tray 601 and equipment earth | ground, another means may be used.

Next, the connection state and insulation state of the tray-carrier conduction toggle 1301 will be described with reference to FIGS.
FIG. 3 is a conceptual diagram illustrating the configuration of the thin film manufacturing apparatus in which the tray-carrier conduction toggle is in a connected state. In FIG. 3, the transport carrier 1201 and the transport tray 601 are at the same potential as the tray-carrier conduction toggle 1301 is inclined to the connection side, and the transport tray 601 is at the same potential as the equipment ground via the transport carrier 1201. It is a schematic diagram which shows a state. FIG. 4 is a conceptual diagram illustrating the configuration of a thin film manufacturing apparatus in which the tray-carrier conduction toggle is in an insulated state.

  As shown in FIGS. 3 and 4, a transport tray 601 is placed on the insulating pad 611 fixed to the transport carrier 1201. When the tray-carrier conduction toggle 1301 is tilted to the connection side, the conductive pins 1311 come into contact with the transport carrier 1201 and the transport tray 601 and the transport carrier 1201 are connected. The transfer carrier 1201 is in contact with the substrate transfer-side transfer rail 401 connected to the equipment ground or the rail transfer wheel 421 connected to the film formation-side transfer rail 411 at the time of going / returning movement. Therefore, the potential of the transport carrier 1201 is the same as the equipment ground. That is, the transport tray 601 and the substrate 701 are at the same potential as the equipment ground via the transport carrier 1201.

  As shown in FIG. 4, when the transport carrier 1201 is transported in the direction of arrival and reaches the end of the film formation side rail 411, the toggle switching shaft 1401 and the tray-carrier conduction toggle 1301 come into contact with each other. The carrier conduction toggle 1301 is inclined to the insulating side, and the conductive pin 1311 is separated from the transport carrier 1201. At this time, since the transfer tray 601 and the substrate 701 are insulated from the transfer carrier 1201 by the insulating pads 611, they are insulated from the equipment ground.

  When the transport carrier 1201 is transported in the return direction and reaches the return end of the substrate loading side transport rail 401 as shown in FIG. 3, the tray-carrier conduction toggle 1301 comes into contact with the toggle switching shaft 1401, The transport tray 601 and the transport carrier 1201 are connected.

When the transport carrier 1201 reaches the return side end after reaching the destination end, the substrate is replaced with the substrate 701 to be processed next, and the same film formation as described above is performed on the substrate 701.
Here, when the transfer is performed on the return side, the transfer carrier 1201 is stopped before reaching the end of the return side, so that the film is repeatedly formed on the same substrate 701 while maintaining the insulating state. Is also possible.

  In this embodiment, the connection or insulation switching means between the transport tray 601 and the transport carrier 1201 by the tray-carrier conduction toggle 1301 does not use an expensive movable cable or an electronic device such as an electromagnetic valve, and the transport carrier 1201. Is a switching means that switches using the inertial force when the is conveyed. However, the means for connecting or insulating the transport tray 601 to the equipment ground is not limited to this configuration.

  An example of a thin film manufacturing method using the thin film manufacturing apparatus configured as described above will be described with reference to the flowchart of FIG. At this time, the thin film manufacturing method in the flowchart of FIG. 2 will be described with reference to FIGS. 1, 5, 6 and 7 as appropriate.

In the following description, reactive sputtering will be described as an example, but this embodiment can also be used for other sputtering.
FIG. 2 is a flowchart for explaining the thin film manufacturing method of the present embodiment. FIG. 5 is a diagram illustrating the stacked state of the thin film of this embodiment. FIG. 6 is a diagram showing the relationship between the discharge power and the temperature during film formation in this embodiment. FIG. 7 is a diagram showing the relationship between the discharge power and the change in temperature and lifetime ratio during film formation in the present embodiment.

First, a general flow of reactive sputtering using a reactive gas at the time of manufacturing a thin film will be described. In FIG. 1, the substrate 701 and the transfer tray 601 are transferred to the substrate loading / unloading vacuum chamber 101 while being placed on the transfer carrier 1201, the loading / unloading gate valve 551 is closed, and the substrate loading / unloading vacuum chamber 101 is closed. Is evacuated by a vacuum evacuation means (not shown) so that the pressure becomes a predetermined vacuum pressure. The predetermined vacuum pressure after evacuation depends on the required film quality, but is, for example, 1 × 10 ⁻⁴ Pa or more and 5 × 10 ⁻³ Pa or less.

  After the substrate loading / unloading vacuum chamber 101 reaches a predetermined vacuum pressure, the gate valve 501 is opened, the transfer tray 1201 is loaded into the film forming vacuum chamber 201, and the gate valve 501 is closed. Thereafter, a sputtering gas and a reactive gas are introduced into the film forming vacuum chamber 201 by using a vacuum exhaust unit and a gas introducing unit (not shown) so that the film forming vacuum chamber 201 has a desired film forming pressure. Then, the degree of vacuum in the film forming vacuum chamber 201 is adjusted. The degree of vacuum in the film forming vacuum chamber is, for example, 0.6 Pa or more and 1.0 Pa or less. For example, Ar (argon) is used as the sputtering gas. As the reactive gas to be introduced, for example, nitrogen is used when forming a nitride film on the substrate 701, and oxygen is used when forming an oxide film on the substrate 701.

  After the sputtering gas and the reactive gas are introduced into the film forming vacuum chamber 201 and reach a predetermined degree of vacuum, the discharge power set in the power source 1101 is input to the electrode 1001 to form a film forming region of the substrate 701. A predetermined film is formed on the substrate 701 by moving the transfer tray 601 in the “bound” direction of FIG. Here, the number of times of passing through the position facing the target 301 to which the discharge power is applied is counted as the number of times of film formation.

  Here, a film forming operation in the case where a 100 nm surface protective film and a nitride film which is an antireflection film are formed on the substrate 701 will be described as an example. The substrate 701 is, for example, a solar cell substrate in which an amorphous silicon film of 10 nm is formed on a silicon substrate having a thickness of 300 μm and 150 mm square. Further, the dimensions and film thicknesses of the silicon substrate, amorphous silicon, and nitride film are examples.

  First, before the first film formation, a first preliminary experiment was performed to determine the discharge power W1 in the first film formation. In the first film formation, in order to perform annealing without causing thermal damage (substrate damage) on the surface of the substrate 701 (the surface of amorphous silicon formed on the silicon substrate), it is necessary to perform heating at around 200 ° C. is there. In order to find a condition that does not cause substrate damage to the surface of the substrate 701, a first preliminary experiment was performed with a plurality of discharge powers with the transfer tray 601 at the same potential as the equipment ground. In the first preliminary experiment, the discharge power of 30 kW was set as the maximum power, and the presence or absence of substrate damage and the substrate temperature during film formation were measured at a transfer speed of 7 mm / s. Here, the reason why the maximum power is set to the discharge power of 30 kW is that this power is a power for which cracking of the silicon target, which was confirmed in another experiment, is concerned. The experimental results of the preliminary experiment are shown in FIG. The discharge power W1 is the first discharge power.

  As shown in FIG. 6, when the discharge power was 10 kW or more, an abnormal discharge trace was confirmed on the substrate 701, and it was found that the substrate was damaged. This is because, since the nitride film of the substrate 701 is an insulating film, when the discharge power increases, a voltage higher than the dielectric breakdown voltage of the nitride film is applied at the initial stage of film formation, and the insulation of the insulating film is broken and abnormal discharge occurs. It is estimated to be. Therefore, the temperature of the substrate 701 was measured only at the time of discharge of 5 kW or less where no abnormal discharge occurred on the substrate 701 (no substrate damage occurred). From the results of FIG. 6, it was found that the discharge power at which no abnormal discharge occurs on the substrate 701 is 5 kW or less, and the discharge power at which the substrate temperature during film formation is around 200 ° C. is 3 kW. When the discharge power was 5 kW, the film thickness obtained by the first film formation was 20 nm, and when the discharge power was 3 kW, the film thickness obtained by the first film formation was 12 nm.

An example of the thin film manufacturing method of the present embodiment based on the result of the first preliminary experiment will be described with reference to the flowchart of FIG.
First, with the tray-carrier conduction toggle 1301 tilted in advance to the connection side, the transport carrier 1201 and the transport tray 601 are set to the same potential, so that the transport tray 601 and the equipment ground are connected to each other via the transport carrier 1201. The potential is set (step S1).

  After step S1, the substrate 701 is placed on the transport tray 601 on the transport carrier 1201 in the substrate loading / unloading vacuum chamber 101, and the loading / unloading gate valve 551 is closed (step S2).

  After step S2, the gate valve 501 is opened, the carrier carrier 1201 on which the substrate 701 and the carrier tray 601 are placed is put into the film forming vacuum chamber 201, and the gate valve 501 is closed. Thereafter, in the state in which the inside of the film forming vacuum chamber 201 is adjusted to 0.9 Pa, which is an example of a predetermined film forming pressure, the first film forming is performed with the discharge power W1 as the first film forming process (step S3). ).

Here, the first discharge power W1 is set to 5 kW or less so that the substrate damage is not caused by the abnormal discharge during the film formation based on the experimental result of the preliminary experiment.
Thermoelectrons are emitted from the plasma generated during film formation. Each thermoelectron is about 10000 ° C. and has a negative potential. For this reason, thermoelectrons are attracted to the equipment ground side, which has a positive potential compared to the negative potential, and the equipment ground and the thermoelectrons collide, so that the temperature of an object at the same potential as the equipment ground rises. . When the transfer tray 601 and the substrate 701 are at the same potential as the equipment ground, thermal electron collisions frequently occur, so that the temperature of the substrate 701 rises and annealing can be performed during film formation.

  After step S3, when the transport carrier 1201 reaches the end of the film-formation-side transport rail 411 (end-of-travel end) in the film-forming vacuum chamber 201, the tray-carrier conduction toggle 1301 contacts the toggle switching shaft 1401. Then, the tray-carrier conduction toggle 1301 is inclined to the non-connection side, so that the transport carrier 1201 and the transport tray 601 are insulated. As a result, the transport tray 601 and the equipment ground can be insulated via the transport carrier 1201 (step S4).

  In this embodiment, after completion of the first (bound) film formation, a nitride film of about several tens of nanometers is formed on the substrate 701, and the second (return) film formation is performed on this nitride film. By doing so, a nitride film of about 80 nm is formed for the purpose of surface protection and antireflection. Here, it is not desirable to deposit a thin film (for example, an oxide film) having a film quality different from that of the nitride film at the interface of the nitride film formed for the first time. This is because, for example, when an oxide film is formed at the interface of the nitride film, the bonding force at the interface is weakened, and there is a concern about peeling of the nitride film.

Therefore, in the present embodiment, the second (return) film formation is performed as the second film formation step with the discharge power W2 within one minute after the completion of the first (outbound) film formation (step S5). ).
In the second film formation, after the first film formation, the vacuum degree of the film formation vacuum chamber 201 was kept at a vacuum state of 0.6 Pa or more and 1.0 Pa or less, which is the degree of vacuum at the time of normal film formation. It is desirable to start.

Here, the reason why the second film formation is performed within 1 minute after the completion of the first film formation is that if the film is left for 1 minute after the film formation, a natural oxide film of about 2 nm or more is formed on the formed surface. This is because it may be formed. That is, if the waiting time between the first film formation and the second film formation is longer than 1 minute, a natural oxide film or the like may be formed on the formed surface.
At this time, if the transport tray 601 and the equipment ground are at the same potential, a standby time longer than 1 minute is required until the substrate temperature after the first film formation is lowered to 200 ° C. or lower.

  Therefore, in this embodiment, by increasing the substrate temperature due to thermionic electrons in the film forming vacuum chamber 201 by insulating the transfer tray 601 and the equipment ground during the second film formation in the above-described step S4. Yes.

  Subsequently, in order to determine the optimum power value of the discharge power W2 for the second film formation, the silicon target is cracked against the substrate 701 on which a 20 nm nitride film is formed at the discharge power of 5 kW in the first film formation. A second preliminary experiment was performed when a nitride film was formed to a thickness of 80 nm with some discharge power, with an upper limit of 30 kW. The change rate of the lifetime obtained in the second preliminary experiment is shown in FIG. Here, the lifetime is related to electrons and holes which are solar cell characteristics, and the lifetime change rate is the lifetime after nitride film formation divided by the lifetime before nitride film formation. It is a value calculated by doing.

  As shown in FIG. 7, when the film is formed at a low power of 3 kW or 5 kW, the change rate of the lifetime is less than 100%, so that the lifetime after the film formation is reduced as compared with that before the film formation. Was confirmed. The reason why the lifetime is reduced after film formation is that it is necessary to slow down the tray conveyance speed in order to form a film with a low power to a predetermined film thickness, and nitrogen, which is a reactive gas for forming a nitride film, This is because a large amount of silicon was implanted into the amorphous silicon film on the substrate surface during the film formation. Here, nitrogen has a property of capturing holes, which are electric carriers, and degrading electric characteristics.

  Conversely, as shown in FIG. 7, it is confirmed that the lifetime change rate after the film formation is improved as the discharge power is increased. This is because, when film formation is performed at high power, the time required for nitrogen implantation into the substrate 701 is shortened as the film formation time per substrate is shortened, so that the influence of lifetime reduction due to nitrogen implantation is reduced. It is thought that. Therefore, it is desirable that the second discharge power W2 be larger than the first discharge power W1 to shorten the nitride film formation time as much as possible.

  Therefore, in this embodiment, the first discharge power is 2 kW to 5 kW, and the second discharge power is 10 kW to 30 kW. Specifically, the first transport speed is 7 mm / s at a maximum discharge power of 5 kW at which the substrate tray 601 is at the same potential as the equipment ground and the substrate damage due to abnormal discharge does not occur. The second transport speed is In the state where the transfer tray 601 is insulated from the equipment ground, the discharge power of 30 kW at which the target 301 is likely to be cracked is 8.8 mm / s.

  The second film formation is started within one minute after the first film formation, but as shown in FIG. 7, even in the film formation with the maximum discharge output of 30 kW, where the silicon target may be broken, The substrate temperature was about 150 ° C., and a nitride film could be formed in a state where the substrate temperature did not rise too much. This is because, since the transport tray 601 is insulated from the equipment ground, the thermoelectrons emitted from the plasma during film formation are not attracted to the transport tray 601 and the collision between the thermoelectrons and the transport tray 601 is alleviated. This is considered to be an effect.

  If a film having a predetermined film thickness can be formed in the second film formation, the film formation is ended here. If more film thickness is required, after step S5 is finished, the transfer tray 601 is insulated from the equipment ground, The discharge power is W, and the third and subsequent film formation steps are performed as the third film formation step, and this process is repeated until a predetermined film thickness is obtained (step S6).

  Note that when the film formation is performed for the third time and thereafter, the film formation is performed in a state where the transfer tray 601 and the equipment ground are insulated. However, when the film formation is performed for the third and subsequent times, the interface of the film to be formed increases, and the possibility of peeling at the interface increases. Therefore, if possible, the film formation is preferably performed twice.

  Here, the case where the film is formed n times in step S6 will be described with reference to FIG. FIG. 5 is a diagram showing a case where a 100-nm nitride film is formed by performing film formation of 5 kW discharge in n times so that the temperature of the substrate does not rise too much.

  In this case, first, Ar (argon) gas and nitrogen gas are each introduced into the film forming vacuum chamber 201 at 100 sccm to adjust the pressure to 1 Pa, and then a transfer tray 601 on which a substrate 701 is mounted is placed. Then, a voltage is applied from the power source 1101 to the silicon target 301 so as to obtain a 5 kW discharge. When a voltage is applied from the power source 1101 to the target 301, plasma is generated in the deposition vacuum chamber 201, a substrate 701 is formed, and thermoelectrons 802 are generated. Then, since the thermoelectrons 802 collide with the transfer tray 601, the substrate 701, and the formed nitride film 801, the temperature of the substrate 701 rises, so that annealing can be performed simultaneously with the film formation. A solar cell substrate can be formed.

  Note that this embodiment solves the problem that the substrate temperature rises excessively when the film is formed in a plurality of times in the conventional configuration, and the film can be formed a plurality of times at around 200 ° C. Therefore, it is effective when forming a nitride film on the solar cell substrate. In addition, when the film is formed in a state where the transfer tray is insulated from the equipment ground so that the substrate temperature does not increase during the film formation, the substrate temperature is 150 ° C. even in the film formation at 30 kW where the silicon target may be cracked. As described below, the lifetime of electrons and holes, which are the solar cell characteristics after sputtering at this substrate temperature, was about 30% as compared to before sputtering. This is predicted to be insufficient annealing of the solar cell substrate. For this reason, when a nitride film is formed on amorphous silicon, it is considered that film formation at around 200 ° C. is desirable.

  In addition, this embodiment solves the problem that an oxide film or the like is formed by allowing sufficient time for substrate cooling to prevent peeling after one film formation, and the peeling easily occurs. The long-term reliability of the solar cell can be ensured because the film can be formed a plurality of times, which is difficult to form. Note that when the substrate temperature reaches 250 ° C., it is desirable that the allowable time for the deposition interval of the substrates is 5 minutes or less per substrate.

  In addition, in order to shorten the time for which the substrate is heated, there is a conventional method in which film formation is performed with high discharge power and the film formation time is shortened, but when the nitride film as an insulating film increases the discharge power, Abnormal discharge occurs in the initial stage of nitride film formation. In our experiment, when the film was formed at 10 kW, abnormal discharge traces were observed on the substrate.

The embodiments of the present invention described above will be described together.
In the thin film manufacturing method of the present invention, the film formation is performed in a plurality of times, and in the first film formation in which the film is directly formed on the substrate, the transfer tray 601 and the equipment ground are at the same potential. Film formation is performed by passing the substrate 701 placed on the tray 601 through a position facing the target 301. Then, the first and second standby times are set within one minute, and in the second and subsequent film formations on the film that has already been formed, the transfer tray 601 and the equipment ground are insulated. Then, film formation is performed with the discharge power set higher than the first discharge voltage. In this way, the lifetime of the first film formation is improved by increasing the substrate temperature by thermoelectrons and performing annealing by making the transport tray 601 and the equipment ground have the same potential, and discharging. By setting the power low, damage to the substrate can be suppressed. Also, by setting the discharge power higher than the first time in the second and subsequent film formation with the transfer tray 601 and the equipment ground insulated, the lifetime change rate can be reduced while enabling the film forming process in a short time. Can be improved. And since the temperature rise of the substrate can be suppressed by performing the second film formation in an insulating state, the standby time between the respective film formations can be shortened, and the different film qualities between the respective films in the standby time Generation of the film can be suppressed, and peeling of the film can be suppressed.

  In the thin film manufacturing apparatus of the present invention, a toggle switching shaft is provided at both ends of the vacuum chamber for film formation, and a tray-carrier conduction toggle for switching connection and insulation between the transfer tray and the equipment ground is provided on the transfer tray. The connection and insulation between the transfer tray 601 and the equipment ground in the thin film manufacturing apparatus can be easily set.

  INDUSTRIAL APPLICABILITY The present invention can suppress film peeling even when forming a film in a plurality of times, and is useful for a thin film manufacturing method and a thin film manufacturing apparatus that form a film on a substrate by sputtering. .

DESCRIPTION OF SYMBOLS 1 1st vacuum vessel 5 Substrate 7 2nd vacuum vessel 9 Deposition measurement means 101 Substrate loading / unloading vacuum chamber 201 Deposition vacuum chamber 301 Target 401 Substrate loading side conveyance rail 411 Deposition side conveyance rail 421 For rail conveyance Wheel 501 Gate valve 551 Gate valve for loading / unloading 601 Transport tray 611 Insulation pad 701 Substrate 801 Nitride film 802 Thermoelectron 901 Arithmetic device 1001 Electrode 1101 Power supply 1201 Transport carrier 1301 Tray carrier conduction toggle 1311 Conductive pin 1401 Toggle switching shaft

Claims (7)

A thin film manufacturing method for forming a film on the substrate by sputtering a substrate mounted on a transport tray at a position facing the target a plurality of times,
A first film forming step of forming a film on the substrate with a first discharge power in a state where the transport tray is connected to an equipment ground;
In a state in which the transfer tray is insulated from the equipment ground, film formation is performed on the film formed in the first film formation step with a second discharge power higher than the first discharge power. And a second film formation step. 2. The thin film manufacturing method according to claim 1, wherein between the first film formation step and the second film formation step, the transfer tray is kept on standby for one minute or less while being insulated from the equipment ground. A third film forming step of performing film formation one or more times on the film formed in the second film forming step with the transfer tray insulated from the equipment ground. The thin film manufacturing method according to claim 1 or 2. 4. The method according to claim 1, wherein the film is a nitride film, the first discharge power is 3 kW or more and less than 5 kW, and the second discharge power is greater than 10 kW and 30 kW or less. A thin film manufacturing method according to claim 1. The thin film manufacturing method according to claim 1, wherein the transfer tray is insulated from the equipment ground in a vacuum state. A thin film manufacturing apparatus for forming a film on a substrate by multiple times of sputtering,
Target,
A rail provided at a position facing the target;
A transfer tray that reciprocates on the rail while the substrate is placed thereon;
A thin-film manufacturing apparatus comprising: a tray-carrier conduction toggle that connects or insulates the transport tray with an equipment ground. A first toggle switching shaft disposed in the vicinity of one end of the rail and in contact with the tray-carrier conduction toggle to insulate the transport tray from an equipment ground during movement of the transport tray;
A second toggle switching shaft disposed near the other end of the rail and contacting the tray-carrier conduction toggle to connect the transport tray to equipment ground while the transport tray is moving. The thin film manufacturing apparatus according to claim 6.

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