JP2006183145A - Method of forming film, film forming apparatus and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To deposit a continuous thin film even when using a highly cohesive metal on a surface of a workpiece having recesses with high aspect ratio. <P>SOLUTION: A film deposition method comprises a step of carrying a substrate in a reaction chamber and mounting the same, a step of feeding a raw gas containing a compound of a first metal into the reaction chamber to thereby cause the surface of the substrate to adsorb the compound of the first metal, a step of bringing the compound of the first metal into contact with a reducing plasma resulting from activation of a reducing gas to thereby obtain a first metal layer, and a step of bringing a target electrode whose at least surface portion consists of a second metal different from the first metal into contact with sputtering plasma and incorporating the thus ejected second metal into the first metal layer to thereby obtain an alloy layer, wherein this sequence of adsorption, reduction and alloy formation steps is carried out one or more times. By this method, even when the cohesive force of the first metal is large, any migration thereof on the substrate is suppressed to thereby realize formation of a continuous thin film of small thickness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a film forming method and a film forming apparatus for forming a metal alloy thin film on a substrate such as a semiconductor wafer, and further relates to a storage medium storing a program for executing the method.

Conventionally, a semiconductor device such as an integrated circuit (IC) has a metal as a conductor in an insulating film formed by a silicon oxide film (SiO2 film) or the like in a semiconductor wafer (hereinafter abbreviated as a wafer) such as a silicon substrate. The wiring is formed so as to be embedded. As a method for forming the wiring, for example, a wiring groove is formed in an insulating film such as a silicon oxide film formed on the surface of the silicon substrate, a metal as a conductor is buried in the wiring groove, and then CMP (Chemical Mechanical Polishing Chemical) is performed. There is known a method of removing an excess metal film by a mechanical mechanical polishing method and flattening a wafer surface. This burying is usually performed by electrolytic plating because the use of CVD (Chemical Vapor Deposition) may cause the surface to become rough and the formed wiring may have different electrical resistances in various places. That is, first, a barrier layer made of titanium nitride (TiN) or the like is formed on the surface of the formed wiring trench by a technique such as CVD using ALD technology or PVD (Physical Vapor Deposition) such as sputtering. This barrier layer has a function of suppressing the permeation of the metal into the insulating film (SiO2) when the metal constituting the wiring is buried later. ALD (Atomic Layer Deposition) is a method of forming a thin film by stacking atomic or molecular layers one by one on the surface of the substrate, and is excellent in controlling the film thickness to be formed. Sputtering is a high vacuum in which high-energy ions such as argon ions are struck against a metal bulk, and metal atoms on the surface of the bulk are struck out in the manner of a ball, and the struck metal atoms are applied to the surface of the substrate. It is a technique of making it adhere in layers.

  Then, a metal thin film called a seed layer is formed on the surface of the barrier layer as an electrode base for electrolytic plating. The seed layer is formed by using sputtering in order to obtain a wiring having a smooth surface as described above. After the seed layer is formed, the wiring trench is filled with the same kind of metal as that constituting the seed layer by electrolytic plating. After the CMP process, an insulating film is further formed on the insulating film in which the wiring trench is formed, and a multilayer wiring structure is formed by repeating similar processes.

  Incidentally, in recent years, with the demand for higher integration and higher speed of semiconductor devices, attempts have been made to reduce the wiring width in addition to forming the multilayer wiring structure as described above. However, new challenges emerged as this trial progressed. Sputtering used when forming a seed layer as described above is a technique in which atoms in a metal bulk are knocked out and scattered to be adsorbed on the substrate surface. Therefore, it is difficult to control the direction in which the atoms are scattered. In other words, when the wiring width becomes smaller and the aspect ratio of the wiring groove (wiring groove depth / wiring groove entrance width) becomes larger, it becomes difficult for metal atoms to efficiently enter the wiring groove and via hole, and the step coverage against them is reduced. And the discontinuity is formed in the seed layer. As described above, when the wiring groove is filled by the electrolytic plating method or the like, the metal constituting the plating does not completely fill the wiring groove, and voids are generated in the formed wiring. Wiring in which voids are generated in this way is stress migration (a phenomenon in which stress acts on the wiring due to the difference in thermal expansion coefficient between the metal wiring and the surrounding insulating film, and metal atoms move in the wiring) and electromigration (A phenomenon in which atoms move as a result of electrons colliding with atoms when current flows in the metal). As a result, disconnection is likely to occur.

  In addition, in order to reduce the influence of the aforementioned stress migration and electromigration caused by reducing the wiring width, instead of Al (aluminum) which has been widely used at present, it has higher strength than Al and has an electric resistance. Wiring is often formed using low Cu (copper).

  However, this Cu has a property that the cohesive force between atoms or molecules is strong. FIG. 6 schematically shows the dynamics of Cu atoms 1 when a seed layer is formed on the surface of the wafer W by PVD. In the initial stage of seed layer formation, Cu atoms 1 are sparsely attached to the surface of the wafer W. However, when the number of Cu atoms 1 attached to the surface of the wafer W increases (FIG. 6A), the Cu atoms 1 are surrounded by the surroundings. The atoms that are present attract each other and aggregate (FIG. 6B). As a result of repeating the aggregation, huge Cu molecules 12 like islands are formed and grown (FIG. 6C). As a result of the island growth, if the amount of Cu supplied to the wafer surface is insufficient, discontinuous points are formed in the seed layer. If discontinuous points are formed, voids are easily formed in the wiring when the wiring grooves are filled by electrolytic plating or the like as described above, and disconnection is likely to occur. For this reason, it is difficult to obtain a seed layer having a small film thickness for the concave portion having a large aspect ratio, and therefore it is difficult to reduce the wiring width.

  The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art. However, when an alloy thin film is obtained from a metal source gas, it is necessary to select a source gas so that different raw materials do not react with each other. It is one of the problems to solve this point because the degree of freedom of the source gas is small.

  That is, an object of the present invention is to provide a technique capable of forming an alloy thin film without considering a combination of metal raw materials. Further, even when a highly cohesive metal is used, a thin film is formed continuously on the surface of a substrate such as a wafer, and further, for example, a film forming method and a film forming apparatus exhibiting high coverage even in a wiring groove having a high aspect ratio, and the method It is providing the storage medium which stored the program which implements.

  The film forming method according to the present invention includes a step of carrying a substrate into a reaction vessel and placing the substrate on a placement unit, and then supplying a source gas containing a first metal compound into the reaction vessel, An adsorption process for adsorbing the first metal compound on the surface of the substrate, and the first metal compound adsorbed on the substrate in contact with the reducing gas while supplying energy for the reduction reaction to the compound A reduction step in which a first metal layer is obtained by reduction, and a sputtering gas is activated on a target electrode that is opposite to the substrate and that is different from the first metal and has at least a surface portion made of the second metal. An alloying step of injecting into the first metal layer a second metal struck out by contacting with the sputtering plasma obtained by converting into a first metal and an alloy layer of the second metal; The adsorption process, reduction process and alloying process And carrying out one or more times a series of cycles consisting of.

  The alloying process is performed, for example, while heating the substrate, and is annealed thereby, so that the second metal diffuses along the first metal. In the present invention, the alloying process is performed, for example, by another apparatus after the alloying process. You may anneal by heating. In the case of a recess having a large aspect ratio by this annealing, the second metal diffuses deeply, but the present invention does not necessarily require the second metal to diffuse. In the reduction process for obtaining the first metal layer, the energy supplied to the compound for the reduction reaction can be exemplified by, for example, the energy of the reduction plasma obtained by activating the reduction gas. It may be thermal energy or light energy. In the method, after the adsorption step, a reduction step and an alloying step may be performed simultaneously. When using a reduction plasma, a plasma in which the reduction plasma and the sputtering plasma are mixed is put in a reaction vessel. It can be implemented by generating. More specifically, one of the parallel plate electrodes and the other electrode are used as a substrate mounting portion and a target electrode, respectively, and the reduction step and the alloying step are performed by applying a high frequency voltage between these electrodes. May be. Further, the present invention can be implemented by pre-coating a second metal layer on the other electrode of the target electrode, for example, a parallel plate electrode. Further, the other electrode has a number of gas supply holes, and is configured to supply the source gas, the reducing gas, and the sputtering gas into the reaction vessel, that is, the gas blowing part is also used. It is preferable to do. The reducing gas can be, for example, hydrogen gas or ammonia gas, and a suitable example of the first metal is copper.

  A film forming apparatus according to the present invention includes a reaction vessel provided with a placement portion for placing a substrate, a heating means for heating the substrate placed on the placement portion, and an inside of the reaction vessel. A source gas supply means for supplying a source gas containing a first metal compound to the substrate and adsorbing the first metal compound on the surface of the substrate; and a first metal compound in the reaction vessel A reducing gas supply means for supplying a reducing gas for reducing the gas, a means for supplying energy for a reduction reaction to the first metal compound adsorbed on the substrate, and a substrate facing the substrate. A target electrode, which is different from the first metal and has at least a surface portion made of the second metal, and a sputtering plasma atmosphere obtained by activating the sputtering gas in order to sputter the target electrode are contained in the reaction vessel. Plastic for forming Generating source, supplying the source gas to the substrate by the source gas supplying unit, reducing the compound with a reducing gas while applying the energy to the first metal compound adsorbed on the substrate, target A series of cycles including the steps of striking a second metal by bringing a sputtering plasma into contact with the electrode and injecting it into the first metal layer to obtain an alloy layer of the first metal and the second metal. And a control unit for controlling each of the means so as to be performed once or more.

  As means for supplying energy for the reduction reaction, plasma generating means, thermal energy generating means, and / or light energy generation for activating the reducing gas to form a reducing plasma atmosphere in the reaction vessel. Means can be mentioned as a preferred example. The substrate mounting portion and the target electrode are also used as, for example, one electrode and the other electrode of parallel plate electrodes, respectively. By applying a high-frequency voltage between these electrodes, the reducing plasma and the sputtering plasma are generated. You may make it let it.

  The present invention can also be realized as a storage medium storing a program for performing the above-described method, and the storage medium of the present invention is a film formation for carrying a film formation process by carrying a substrate into a reaction vessel. A computer program used in the apparatus, which stores a program for executing the method of the present invention. Specifically, the program includes a group of instructions for performing the above steps.

  According to the present invention, the first metal is adsorbed on the substrate surface using the source gas, and then the second metal is adhered to the substrate by sputtering and alloyed. Therefore, an alloy thin film can be easily obtained. For example, it can be applied to the formation of the wiring itself. For example, when an alloy thin film is formed in the recess, the first metal is adsorbed to the bottom even if the aspect ratio of the recess is large. Next, the second metal by sputtering adheres in the recess. However, by heating and annealing the substrate, the second metal diffuses along the first metal. As a result, the alloy thin film reaches the bottom of the recess. This is superior to the thin film formation method using only sputtering in this respect. Even when the cohesive force of the first metal is strong, such as Cu, the movement of the first metal on the substrate surface is suppressed by forming an alloy with the second metal. As a result, a metal thin film (alloy thin film) containing the first metal can be formed with a small film thickness.

  Therefore, the utility value of the present invention is great. For example, as a method for forming a seed layer in a recess in order to form a wiring layer of a semiconductor device by plating, a continuous seed layer having a small film thickness can be formed by applying the method according to the present invention. Therefore, generation of voids in the wiring can be suppressed when the wiring is formed by plating the formed seed layer.

  FIG. 1 shows an example of a film forming apparatus for carrying out the film forming method according to the present invention. The apparatus is a film forming apparatus for forming a seed layer made of Cu (copper) on the surface of a wafer W as an object to be processed. First, the entire structure of the film forming apparatus will be described. In the figure, reference numeral 2 denotes a processing container, and a recess 20 is formed in the center of the bottom surface. An exhaust port 21 is formed in the side wall of the recess 20, and the exhaust port 21 communicates with a vacuum pump 23 that constitutes a vacuum exhaust unit together with the pressure adjustment unit 22 via the pressure adjustment unit 22. The pressure adjusting unit 22 can maintain the inside of the processing container 2 at a predetermined vacuum pressure by adjusting the opening of a valve, for example, by a control signal from the control unit 5 described later. Further, an opening 24 is formed in the side wall of the processing container 2 so that a transfer arm (not shown) can enter when the wafer W is delivered, and can be opened and closed by a gate valve G. A heater 25 is embedded in the wall portion of the processing container 2 and is made of, for example, a resistance heating element, and the amount of heat generated is controlled by the control unit 5 described later.

  In the processing container 2, a mounting table 3 configured as a substrate mounting unit is supported and provided via a support unit 31. The mounting table 3 is made of, for example, aluminum and has a cylindrical shape, and the upper surface can hold the wafer W by suction by an electrostatic chuck (not shown). Inside the mounting table 3 is provided a temperature control means 32 that combines a heating means such as a heater and a refrigerant flow path. The wafer W is preset by the heat generation of the plasma and the temperature control action of the temperature control means 32. Maintained at temperature. In addition, for example, three lift pins 33 for transferring the wafer W to and from a transfer arm (not shown) are provided inside the mounting table 3. The lift pin 33 is freely projectable and retractable, and its elevation is performed by the function of the elevation mechanism 35 via a support member 34 that supports the lower end of the lift pin 33.

  Inside the processing container 2, a gas shower head 23 as a gas supply unit is provided on the upper side via an insulating member 2a made of, for example, ceramics and a support 2b. The first and second gas supply pipes 4a and 4b are connected to the ceiling of the gas shower head 23, and a number of gas supply holes 2c are formed on the lower surface side. The gas from 4a and the second gas supply pipe 4b is dispersed from the gas supply hole 2c and supplied to the processing atmosphere without intermingling with each other via the gas flow paths 27 and 28, respectively.

  A high frequency power source 23b is connected to the gas shower head 23 via a matching unit 23a. The high frequency power supply unit 23 b is connected to the control unit 5 described later, and is configured such that power is controlled based on a control signal from the control unit 5. On the other hand, the mounting table 3 is grounded, for example, so that a high-frequency voltage from the matching unit 23b is applied between the gas shower head 23 and the mounting table 3 so that the processing gas can be converted into plasma. In this example, the high frequency power supply unit 23b and the matching unit 23a correspond to plasma generating means for generating reducing plasma and plasma generating means for generating sputtering plasma. FIG. 2 is an enlarged view of the gas shower head 23. On the lower surface of the gas shower head 23, a coating layer 2 d pre-coated with a second metal, for example, Ni (nickel) is formed so as to face the mounting table 3. Here, the pre-coating means that a desired metal is coated in advance by CVD, ALD, plating, thermal spraying, or the like. As described above, when electric power is supplied to the gas shower head 23, the coating layer 2 d functions as a target electrode (cathode) when sputtering is performed in the processing container 2. In order to enhance the action as the cathode, a negative DC power source 23c may be applied to the target electrode in addition to the high-frequency power source unit 23b as shown by a broken line in FIG.

  Subsequently, the gas supply system will be described. The upstream side of the first gas supply pipe 4a connected to the ceiling portion of the gas shower head 23 branches in the middle, and one end thereof is connected via the gas supply device group 41. A gas supply source 42 that supplies Ar gas, which is a sputtering gas, is connected. The other end of the first gas supply pipe 4a is connected via a gas supply device group 43 to a gas supply source 44 that supplies H2 (hydrogen) gas for reducing the first metal compound. For example, valves and a mass flow controller (hereinafter abbreviated as MFC) are incorporated in the gas supply device groups 41 and 43, and Ar gas from the gas supply source 42 and the gas supply source 44 are controlled by a control signal from the control unit 5. H2 gas supply / disconnection and flow rate are controlled. In addition to H2, a gas such as NH3 (ammonia), N2H4 (hydrazine), NH (CH3) 2 (dimethylamine), N2O (dinitrogen monoxide) may be used as the reducing gas. In this example, the gas supply device group 43 and the gas shower head 23 correspond to a reducing gas supply means.

  A gas supply device group 45 is connected to the upstream side of the second gas supply pipe 4 b connected to the ceiling portion of the gas shower head 23. A carrier gas supply unit 46 such as Ar is connected to the gas supply device group 45 through a gas supply pipe 4c, and a liquid source supply tank 47 as a liquid source supply source is connected through a liquid source supply pipe 4d. ing. The liquid source supply tank 47 stores Bis (6-ethyl-2,2-dimethyl-3,5-decanedionato) copper (hereinafter referred to as Cu (edmdd) 2), which is a liquid of the first metal compound. Has been. The gas supply device group 45 incorporates, for example, a vaporizer, a liquid mass flow controller (LMFC), a gas mass flow controller MFC, a valve, and the like, and the operation of each unit is controlled by the control unit 5 described later. In addition, as a compound of Cu which is the first metal, instead of Cu (edmdd) 2, Cu (hfac) 2 or a metal compound in which Cu similar to Cu (hfac) 2 and a β-diketone compound are combined. Alternatively, metal carboxylic acid complexes such as Cu (CH3COO) 2 and Cu (CF3COO) 2 may be used as the metal source. In this example, the gas supply device group 45 and the liquid source supply tank 47 correspond to source gas supply means.

  In this film forming apparatus, for example, a control unit 5 including a computer is provided, and includes a program 51, a memory, a data processing unit including a CPU, and the like. The program 51 includes an instruction so that a seed layer can be formed as described in the operation of the device described later. In addition, for example, the memory has an area in which processing parameter values such as processing pressure, processing time, gas flow rate, and power value are written, and when the CPU executes each instruction of the program 51, these processing parameters are read out. Then, a control signal corresponding to the parameter value is sent to each part. This program (including a program related to the process parameter input screen) is stored in a storage medium such as a flexible disk, a compact disk, or an MO (magneto-optical disk) and installed in the control unit 5.

  Next, a process of forming a seed layer made of Cu and Ni (nickel) in a wiring groove and a via hole, which are recesses formed on the surface of the wafer W, using the above-described apparatus, and further forming a wiring is shown in FIGS. This will be described with reference to FIG. First, the state of the wafer W before the processing by the apparatus is started will be described. As shown in FIG. 3A, the surface of the wafer W is further wired on the wiring layer forming a part of the semiconductor integrated circuit. In order to form a layer, an insulating film 61 such as SiO2 is formed, and a wiring groove 6a and a via hole 6b are formed in the insulating film, and a wafer W including a recess made of the wiring groove 6a and the via hole 6b is formed. The surface is already covered with a barrier layer 62 made of TiN, for example.

  In the above-described apparatus, first, the gate valve G is opened, and the wafer W is loaded into the processing chamber 2 by a transfer arm (not shown), and the wafer W is placed horizontally on the mounting table 3. After the transfer arm has been withdrawn from the processing container 2, the gate valve G is closed, and then the inside of the processing container 2 is evacuated by the vacuum pump 23 through the exhaust port 21, so that the internal pressure becomes 133 Pa (1 Torr), for example. Maintained. At this time, the surface of the mounting table 3 is heated to the process temperature, for example, 150 ° C. by the temperature adjusting means 32, and the temperature in the processing container 2 is maintained at, for example, about 50 to 120 ° C. by the heater 25. Thereafter, the following steps are performed.

(Step 1: Feed the raw material into the processing container 2)
He gas is supplied into the liquid source supply tank 47, and the raw material made of Cu (edmdd) 2 stored in the tank 47 flows into the gas supply device group 45 at a flow rate of 0.05 to 3 ml / second, for example. In the gas supply device group 45, Cu (edmdd) 2 is vaporized to become a raw material gas, and the raw material gas flows through the gas supply pipe 4b and is supplied into the processing container 2 through the gas shower head 23 together with the carrier gas. Is done. As schematically shown in FIG. 4A, the Cu (edmdd) 2 molecule 7 in the processing gas supplied into the processing container 2 is, for example, the surface of the barrier layer 62 of the wafer W heated to 140 ° C. For example, a molecular layer of several molecules to several tens of molecules is formed.

(Step 2: Purge and exhaust in the processing vessel)
After the supply of Cu (edmdd) 2 gas into the processing container 2 is stopped, the purge gas such as Ar gas is evacuated while being supplied into the processing container 2, and then the supply of the purge gas is stopped, for example, the pressure adjusting unit 22. The butterfly valve is fully opened to bring the inside of the processing container 2 into a cut-off state, and thus Cu (edmdd) 2 gas that has not been adsorbed by the barrier layer 62 is removed from the processing container 2. The reason for supplying the purge gas in this way is to increase the exhaust efficiency by extruding the source gas with the purge gas.

(Step 3: Reduction of raw materials and sputtering)
Then, H 2 gas from the gas supply source 44 and Ar gas from the gas supply source 42 are supplied into the processing container 2 through the gas supply pipe 4 a and the gas shower head 23. Then, a high frequency voltage is applied between the gas shower head 23 as the upper electrode and the mounting table 3 as the lower electrode by the high frequency power supply unit 23b, and Ar as the sputtering gas is turned into plasma (activated) to generate plasma for sputtering. Is generated, and the H 2 gas, which is a reducing gas, is turned into plasma, and reducing plasma is generated. FIG. 4B schematically shows a reaction occurring in the processing container 2 in a state where plasma is generated. Active species such as hydrogen ions 71 and hydrogen radicals (not shown) in the plasma react with Cu (edmdd) 2 molecules 7 on the surface of the barrier layer 62 to reduce the molecules, and Cu atoms 7a are formed on the surface of the barrier layer 62. And edmdd constituting the Cu (edmdd) 2 molecule 7 is scattered into the gas phase of the processing vessel 2 as indicated by reference numeral 7b in the figure. That is, the Cu (edmdd) 2 molecule 7 is reduced by the reducing gas H2 gas and plasma energy added to the reaction system (in this example, added to hydrogen gas).

  On the other hand, Ar + ions 72 collide with the coating layer 2d of the gas shower head 23 and sputter Ni atoms 73 constituting the coating layer. The sputtered Ni atoms 73 are injected into the Cu layer, and an alloy is formed by solid solution or bonding with the Cu atoms 7a. When the aspect ratio of the recess where the seed layer is to be formed is large, the Ni atoms 73 may not be able to be achieved deep inside the recess. However, since the wafer W is heated, Ni is annealed so to speak. Then, it diffuses along the surface of the Cu layer, and as a result, it is injected into the Cu layer up to the bottom surface of the recess. Here, the state of the Ni atom 73 and the Cu atom 7a is not limited to the case where the Ni atom 73 collides with the Cu atom 7a after the Cu (edmdd) 2 molecule 7 is reduced, but Cu (( Even when Ni atoms 73 collide with edmdd) 2 molecule 7, since the amount of Ni sputtering is small, the Cu (edmdd) 2 molecule 7 is reduced by hydrogen plasma, and the Ni73 and Cu7a are combined or dissolved. It becomes a state. Therefore, the reduction treatment of Cu (edmdd) 2 molecules 7 and the sputtering treatment of Ni may not be performed at the same time, but may be performed before and after each other. That is, one of the H2 gas and Ar gas is supplied first to generate a plasma in the processing vessel 2 to cause a reaction, and after the other gas is supplied, a plasma is generated again to react. You may wake up. Further, the reducing gas and the sputtering gas may be the same. For example, when H2 gas is used as these gases and the power of the high-frequency power supply unit 23b is increased, the reduction of the source gas adsorbed by the plasma H2 gas and the sputtering of the target can occur simultaneously.

(Step 4: Purge and exhaust in the processing vessel)
After the generation of plasma is stopped by turning off the high frequency power supply unit 23b, supply of purge gas and evacuation are performed in the same manner as in Step 2 described above, and molecules and atoms not adsorbed on the barrier layer 62 are removed from the processing vessel 2 Remove.

  In such a series of steps 1 to 4, for example, step 1 is performed for 1 second, step 2 is performed for 1 second, step 3 is performed for 1 second, and step 4 is performed for 1 second. Thereafter, in steps 1 to 4, the surface of the barrier layer 62 is completely covered with Cu atoms 7a and Ni atoms 73, that is, a Cu-Ni alloy layer, as shown in FIG. Repeat until The number of repetitions is, for example, about 5 to 100 times, and the thickness of the seed layer 63 is, for example, about 5 to 10 nm. FIG. 3B shows the state in which the seed layer 63 is formed in the entire wiring trench 6a and the via hole 6b. Thereafter, Cu is deposited on the wafer W by, for example, electrolytic plating to fill the recesses with the wiring grooves 6a and via holes 6b, and the surface is planarized by CMP, as shown in FIG. 3C. Then, a wiring 64 made of Cu is formed.

  According to the above-described embodiment, the so-called ALD (Atomic Layer Deposition) method of adsorbing the molecular layer of the Cu compound on the surface of the wafer W is utilized, and this is reduced to deposit Cu in the recess. Even if the recess has a large aspect ratio, Cu can be supplied to the bottom. Ni is adhered to Cu by sputtering, but as described above, Ni diffuses through the Cu layer, so that it reaches the bottom of the recess, that is, a Cu-Ni alloy with good step coverage (step coverage). A seed layer consisting of layers is formed.

  And the movement of Cu atom is suppressed by Ni atom by alloying by the coupling | bonding of Cu atom and Ni atom. Therefore, aggregation of Cu atoms and island-like growth of Cu molecules are suppressed, so that the seed layer 63 can be formed as a continuous film. Therefore, by subsequently embedding Cu, it is possible to suppress the generation of voids in the wiring 64 when the wiring 64 is formed, so that the wiring 64 can have high reliability. In the above example, the reducing gas H2 gas and the plasma energy are used to reduce the Cu (edmdd) 2 molecule 7, but the energy applied to the reaction system for the reduction is the plasma energy. For example, the wafer W may be heated to a temperature necessary for reduction to supply thermal energy, or may be irradiated with light to apply light energy.

  Further, in diffusing Ni into the recess by annealing, in the above example, the wafer W is heated and Ni is diffused by the heat. However, it is not always necessary to heat the wafer W. For example, in order to anneal Ni, after a series of steps is completed, the wafer W may be separately heated, or the wafer W may be irradiated with laser light. In this embodiment, since sputtered Ni is implanted into the Cu layer, it is possible for Ni to diffuse through the Cu layer to the depth of the recess. Unlike the case where the Cu seed layer is formed by sputtering, it is based on the idea of combining the reduction process of Cu (edmdd) 2 molecules 7 and the process of sputtering Ni.

  In the present embodiment, film formation was performed using Cu as the first metal, but the first metal is not limited to Cu, and Ti (titanium), Sn (tin), W (tungsten), Ta (tantalum), Metals such as Mg (magnesium), In (indium), Al (aluminum), Ag (silver), Co (cobalt), Nb (niobium), B (boron), V (vanadium), Mn (manganese) are preferably used. It is done. The second metal is not limited to Ni in the above embodiment, and can be selected from the metals. However, for the second metal, it is preferable to use a metal having a higher melting point than the first metal or a metal having the same melting point in order to efficiently suppress aggregation of the first metal atoms. Further, the seed layer 63 may be made of an alloy composed of three or more kinds of metals in addition to the above-described alloy in which two kinds of metals such as Cu and Ni are bonded. That is, for example, after the second metal is adhered to the wafer surface and evacuation is performed, the third metal may be further adsorbed on the wafer surface by sputtering to form an alloy composed of three kinds of metals on the wafer surface.

In the present embodiment, instead of the upper electrode facing the mounting table 3 also serving as a gas shower head for supplying gas, a gas supply port is provided separately from the upper electrode, for example, on the side wall of the reaction vessel 2. Also good. Furthermore, even if the target electrode is not formed by pre-coating the second metal on the lower surface of the upper electrode, the material of the upper electrode itself may be composed of the second metal, but if the pre-coating is performed, the pre-coated portion disappears. After that, there is an advantage that it is not necessary to replace the entire electrode because it only needs to be precoated again. Note that the present embodiment is not limited to the formation of the seed layer, and may be, for example, the case where the entire wiring layer is formed or the case where a thin film of another alloy is formed. Further, the electrode for making the reducing gas and the sputtering gas into plasma and the target electrode may be separate, and in this case, for example, in a device using an inductively coupled plasma system, the target electrode is arranged opposite to the mounting table. Can be mentioned.
The substrate in the present invention is not limited to a wafer as in the above-described embodiment, and may be a glass substrate for a flat panel used in a liquid crystal display or a plasma display, a ceramic substrate, or the like.

  Next, in order to confirm the effect of the present invention, a seed layer was formed on the surface of the bare silicon wafer by using the film forming apparatus described in detail in the embodiment. Cu (edmdd) 2 was used as the first metal compound, and Ni was used as the second metal. Experiments were performed by generating a reducing plasma using H2 gas as the reducing gas and generating a sputtering plasma using Ar gas as the sputtering gas. Three seed layers were obtained by changing the sputtering conditions without changing the Cu film formation conditions. The Ni content (atomic%) in the seed layer of each layer is 9 atomic%, 17 atomic%, and 36 atomic%, respectively. In addition, a seed layer in which Ni is not sputtered (a seed layer in which Ni is 0 atomic% was used as a comparative example, and the state of the wafer surface in each of these examples was photographed using a scanning electron microscope (SEM).

  Images taken in the comparative example and Examples 1 to 3 are shown in FIGS. Further, sheet resistance (Rs (unit: Ω / sq)) was measured by a four-probe measurement method for the seed layer formed in the comparative example and each of Examples 1 to 3. The specific resistance (ρs (unit: μΩ · cm)) was calculated using the sheet resistance and the film thickness obtained by fluorescent X-ray analysis (XRF). The results are also shown in FIG.

  In the displayed images, the upper row is an image obtained by photographing the wafer surface from the side, and the lower row is an enlarged image of the wafer surface. 5B to 5D, it can be seen that the metal is densely spread on the wafer surface in each example. Further, it can be seen that the surface of the wafer in the comparative example is severely uneven because Cu is agglomerated into macromolecules as shown in FIG. Further, as shown in FIG. 5, the sheet resistance of the wafer in each example could be measured, but the sheet resistance of the wafer in the comparative example could not be measured. That is, the seed layer in each example is formed as a continuous film, but the seed layer in the comparative example is a discontinuous film. Therefore, it has been proved that the use of the method and apparatus according to the present invention can suppress the occurrence of discontinuous points when forming the seed layer.

It is the vertical side view which showed one Embodiment of the film-forming apparatus which concerns on this invention. It is an enlarged view of the shower head which comprises the said film-forming apparatus. FIG. 4 is a process diagram for forming wirings in wiring grooves and via holes on the surface of the wafer W using the film forming apparatus. It is the schematic diagram which showed the formation process of the seed layer at the time of forming the said wiring. It is an enlarged view of the metal layer formed on the surface of the wafer W using the said film-forming apparatus. It is the schematic diagram which showed the dynamics of Cu when forming into a film on the surface of the wafer W using Cu.

Explanation of symbols

W Wafer 2 Processing vessel 23 Gas shower head 3 Mounting table 5 Control unit 62 Barrier layer 63 Seed layer (Cu—Ni alloy layer)
7 Cu (edmdd) 2 molecule (Cu compound)
73 Ni atom

Claims (17)

Carrying the substrate into the reaction vessel and placing it on the placement unit;
Next, an adsorption step of supplying a source gas containing a first metal compound into the reaction vessel to adsorb the first metal compound on the surface of the substrate;
A reduction step of reducing the first metal compound adsorbed on the substrate by bringing it into contact with a reducing gas while supplying energy for the reduction reaction to the compound to obtain a first metal layer;
A second electrode that is opposed to the substrate and is sputtered by bringing a sputtering plasma obtained by activating the sputtering gas into contact with a target electrode that is different from the first metal and has at least a surface portion made of the second metal. And injecting the metal into the first metal layer to obtain an alloy layer of the first metal and the second metal,
A film forming method comprising performing a series of cycles including the adsorption step, the reduction step, and the alloying step one or more times.   The film forming method according to claim 1, wherein the alloying step is performed while heating the substrate.   In the reduction step for obtaining the first metal layer, the energy supplied to the compound for the reduction reaction is the energy, thermal energy, and / or light energy of the reducing plasma obtained by activating the reducing gas. The film forming method according to claim 1, wherein:   The film forming method according to claim 1, wherein a reduction step and an alloying step are simultaneously performed after the adsorption step.   The one of the parallel plate electrodes and the other electrode are used as a mounting portion and a target electrode, respectively, and the reduction step and the adsorption step are performed by applying a high frequency voltage between the electrodes. 5. The film forming method according to any one of 1 to 4.   6. The film forming method according to claim 1, wherein a second metal layer is precoated on the target electrode.   7. The other electrode has a plurality of gas supply holes formed therein, and is configured to supply the source gas, the reducing gas, and the sputtering gas into the reaction vessel. The film-forming method of description.   8. The film forming method according to claim 1, wherein a step of exhausting the inside of the reaction vessel is performed following the adsorption step.   The film forming method according to claim 1, wherein the series of cycles is performed a plurality of times, and a step of evacuating the reaction vessel is performed between the cycles.   The film forming method according to claim 1, wherein the reducing gas is hydrogen gas or ammonia gas.   The film forming method according to claim 1, wherein the first metal is copper. A reaction vessel provided with a placement portion for placing a substrate;
A heating means for heating the substrate placed on the placement portion;
A source gas supply means for supplying a source gas containing a first metal compound into the reaction vessel to adsorb the first metal compound on the surface of the substrate;
A reducing gas supply means for supplying a reducing gas for reducing the first metal compound into the reaction vessel;
Means for supplying energy for a reduction reaction to the first metal compound adsorbed on the substrate;
A target electrode facing the substrate and different from the first metal, at least the surface portion being made of the second metal;
Plasma generating means for forming a sputtering plasma atmosphere in a reaction vessel obtained by activating a sputtering gas to sputter the target electrode;
Supplying the source gas to the substrate by the source gas supply means; reducing the compound with a reducing gas while applying the energy to the first metal compound adsorbed on the substrate; A series of cycles including the step of knocking out the second metal by contacting the plasma and injecting it into the first metal layer to obtain an alloy layer of the first metal and the second metal is performed once or more. And a control unit for controlling each of the means as described above.   The step of reducing the compound of the first metal and the step of injecting the second metal into the first metal layer to obtain an alloy layer of the first metal and the second metal are performed simultaneously. The film forming apparatus according to claim 12.   The means for supplying energy for the reduction reaction includes plasma generating means, thermal energy generating means, and / or light energy generating means for activating the reducing gas to form a reducing plasma atmosphere in the reaction vessel. 14. The film forming apparatus according to claim 12, wherein the film forming apparatus is a film forming apparatus. The mounting part of the substrate and the target electrode also serve as one electrode and the other electrode of the parallel plate electrodes, respectively.
The plasma generating means for forming the reducing plasma atmosphere and the plasma generating means for forming the sputtering plasma atmosphere are used together, and a high frequency power supply unit for applying a high frequency voltage between the parallel plate electrodes is provided. The film forming apparatus according to any one of claims 12 to 14.   The film forming apparatus according to claim 12, wherein the target electrode is precoated with a second metal layer.   A computer program for use in a film forming apparatus for carrying a substrate into a reaction vessel and performing a film forming process, the program for performing the process according to any one of claims 1 to 11. The storage medium characterized by storing.

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