JP5535756B2 - Sputtering method and sputtering apparatus - Google Patents

Description

  The present invention relates to a sputtering method for embedding a metal material in a recess formed in an insulating film, and a sputtering apparatus used in the sputtering method.

  2. Description of the Related Art Conventionally, in a semiconductor device, a multilayer wiring structure in which a plurality of wirings are connected by via plugs has been widely used for the purpose of increasing functionality and reducing the size. In recent years, via plugs have been miniaturized in response to miniaturization of multilayer wiring structures, and current density has increased due to this miniaturization, and electromigration has become serious.

  As a proposal for reducing electromigration, for example, as described in Patent Document 1, a two-step sputtering method in which a via plug is formed by two sputtering processes is known. In the two-step sputtering method, a liner layer made of crystal grains having a small grain size is first formed on the entire inner surface of the via hole, and then a bulk layer made of crystal grains having a large grain size is embedded inside the liner layer by heating. According to such a two-step sputtering method, the boundaries of crystal grains constituting the via plug are easily aligned in a direction parallel to the extending direction of the via plug, and are difficult to align in the direction perpendicular to the extending direction of the via plug. As a result, electromigration due to the boundary direction of crystal grains and the direction of current is suppressed, and the reliability of the semiconductor device having the multilayer wiring structure can be improved.

JP 2000-260770 A

  By the way, the liner layer and the bulk layer formed by the two-step sputtering method require the following different film forming conditions in order to improve the embedding property in the via hole. First, for the liner layer formed on the entire inner surface of the via hole, high coverage of the liner layer itself and a low film formation temperature for obtaining a particle size smaller than that of the bulk layer are required. Next, for the bulk layer laminated on the liner layer, a grain size larger than that of the liner layer and a high film formation temperature for crystal grains to flow on the liner layer are required. Therefore, in the above-described two-step sputtering method, the liner layer and the bulk layer are formed by two types of sputtering apparatuses having different sputtering methods.

  As a sputtering apparatus for forming the liner layer, there is a so-called long throw method in which the TS distance, which is the distance between the target and the substrate, is increased and the particles sputtered from the target fly substantially perpendicular to the substrate. It has been adopted. In addition, a method in which the substrate is not heated when the liner layer is formed is also used. According to these systems, since the sputtered particles fly substantially perpendicular to the bottom surface of the via hole, the liner layer itself has a high covering property. In addition, for example, the substrate temperature is maintained at a low temperature of 200 ° C. or lower, so that the sputtered particles attached to the insulating film are difficult to grow as crystal grains, and the grain size of the crystal grains constituting the liner layer is relatively small. Get smaller.

On the other hand, as a sputtering apparatus for forming a bulk layer, a so-called reflow method is employed in which a crystal is flowed by heating a substrate during the formation of the bulk layer. In addition, a method in which the TS distance is shortened so that particles flying in various directions are attached to the substrate. According to these methods, since the temperature of the substrate is maintained at a high temperature of 400 ° C., for example, crystal grains having a grain size larger than the crystal grains constituting the liner layer are formed on the liner layer. And as a result of the fluidity being expressed in the crystal grains constituting the upper layer, the crystal grains constituting the bulk layer are located near the opening of the via hole or the inner peripheral surface of the via hole regardless of the direction in which the sputtered particles flew. It flows toward the bottom of the via hole and fills the entire inside of the via hole.

  However, when two different sputtering methods are employed to form the liner layer and the bulk layer, at least two separate sputtering devices suitable for the sputtering method are required. In addition, in order to avoid the liner layer from being exposed to the atmosphere before forming the bulk layer, it is necessary to connect the two sputtering apparatuses by another vacuum apparatus such as a vacuum transfer chamber. As a result, the size and complexity of the apparatus for manufacturing the semiconductor device cannot be avoided.

  In addition, the problem of increasing the size and complexity of the manufacturing apparatus is a problem that can occur in a device for forming a contact plug for connecting an active element and a wiring in addition to the via plug, and the long throw method and the reflow method are used. This is a problem that is generally common to devices that use and form a single wiring element.

  The present invention has been made in view of the above-described conventional situation, and an object thereof is a sputtering method capable of improving the embedding property when a metal material is embedded in a recess by a single sputtering apparatus, and the sputtering method. An object of the present invention is to provide a sputtering apparatus used for the above.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to the first aspect of the present invention, the inside of the concave portion of the substrate disposed in the vacuum chamber is formed by sputtering a metal target provided in the vacuum chamber with ions in the plasma generated in the vacuum chamber. In the sputtering method of embedding a metal material in the substrate, a first step of sputtering the metal target while applying a bias voltage to the substrate, and a second step of sputtering the metal target without applying a bias voltage to the substrate. Are sequentially executed in the vacuum chamber, and in the first step, the metal target is sputtered with a pressure at which the metal particles emitted from the metal target and the charged particles in the plasma collide with each other. In the second step, the charged metal particles are drawn toward the inside of the recess by the bias voltage. The temperature of the substrate to be higher than the first step so that the metal particles adhering to the substrate to flow into the recess by sputtering the metal target, be a target for the metal target comprising aluminum The distance between the metal target and the substrate is not less than 30 mm and not more than 90 mm. In the first step, a bias voltage is applied to the substrate by supplying high frequency power having a frequency of 13.56 MHz to the substrate. The pressure in the vacuum chamber is 5 Pa or more and 50 Pa or less, the temperature of the substrate is 20 ° C. or more and 200 ° C. or less, and the high frequency power is 7 × 10 ⁻⁴ W / mm ² or more and 7 × 10 ^{−. 3} / mm ² or less, wherein in the second step, the pressure in the vacuum chamber is less and 0.5Pa or 0.01 Pa, the substrate temperature There as its gist to or less than and 450 ° C. or higher 350 ° C..

  According to the sputtering method of the present invention, in the first step, the sputtered metal particles collide with charged particles in the plasma to become charged metal particles. Although the metal particles lose directivity due to multiple scattering in the plasma, the metal particles fly toward the inside of the recesses provided in the substrate by the bias voltage applied to the substrate. As a result, the metal particles easily reach the bottom of the recess provided in the substrate, and the coverage of the metal particles on the inner surface of the recess is improved. On the other hand, in the second step, film formation is performed in a state where no bias voltage is applied to the substrate, so that ions in the plasma are attracted by the bias voltage and sputter metal particles adhering to the substrate. Spatter is suppressed. As a result, the film formation rate in the second step is higher than the film formation rate in the first step.

And since the temperature of the board | substrate in a 1st process is lower than the temperature of the board | substrate in a 2nd process, so that the particle size of the metal particle adhering in a recessed part may mutually differ in a 1st process and a 2nd process. Become. In addition, since the temperature of the substrate in the second step is a temperature at which the metal particles flow into the recess, the grain size of the crystal grains in the metal film formed in the recess in the first step is the second It becomes smaller than the grain size of the crystal grains in the metal film formed in the process. As a result, the fluidity of the metal particles adhered in the second step is promoted at the interface between the metal film formed in the first step and the metal film formed in the second step, so that It becomes easy to embed a metal material in.

Thus, according to the sputtering method of the present invention, when a metal material is embedded in the recess using a single sputtering apparatus, it is possible to improve the embedding property of the metal material.
Moreover, according to this invention, the distance of the target and board | substrate which is a flight distance of a metal particle is 30 mm or more and 90 mm or less, and the pressure in a 1st process is 5 Pa or more and 50 Pa or less. The collision frequency between the metal particles emitted from the target and the charged particles in the plasma increases as the distance between the target and the substrate increases and the pressure in the vacuum chamber increases. In addition, the charged metal particles are more easily attracted by the bias voltage applied to the substrate as the distance between the target and the substrate becomes shorter. In this regard, in the above sputtering method, the pressure in the vacuum chamber, the distance between the target and the substrate, and the supply amount of the high frequency power in the first step are set in the above range, so that the discharged metal Collisions between particles and charged particles and entrainment of charged metal particles occur more reliably.
The distance between the target and the substrate, which is the flight distance of the metal particles, is 30 mm or more and 90 mm or less, and the pressure in the vacuum chamber in the second step is 0.01 Pa or more and 0.5 Pa or less. The frequency of arrival of the metal particles emitted from the target to the surface of the substrate becomes so high that the metal particles emitted from the target are not scattered by the gas staying in the vacuum chamber. In this respect, in the sputtering method, the number of collisions between the sputtered particles and the various particles in the vacuum chamber can be suppressed and the film formation rate can be improved while securing the number of particles to be sputtered by the target.
In addition, since the temperature of the substrate in the first step is 20 ° C. or higher and 200 ° C. or lower, the increase in the particle diameter of the aluminum-containing film formed in the first step is suppressed. Further, since the temperature of the substrate in the second step is 350 ° C. or higher and 450 ° C. or lower, the fluidity of the aluminum-containing film formed in the second step can be surely expressed.

According to a second aspect of the present invention, in the sputtering method according to the first aspect, the substrate is electrostatically adsorbed by being provided in the vacuum chamber, and the substrate is heated with an amount of heat corresponding to the adsorption force. In the first step, a first DC voltage is applied to the electrode of the electrostatic chuck. In the second step, the first DC voltage is applied to the electrode of the electrostatic chuck. The gist is to make the temperature of the substrate higher than that of the first step by applying a higher second DC voltage.

  In general, as a heating mechanism for heating a substrate in a vacuum chamber, a heater for heating the substrate is mounted on an electrostatic chuck that electrostatically attracts the substrate, and mechanical contact between the substrate and the electrostatic chuck is performed. It is known to apply heat to the substrate. According to the present invention, when a DC voltage higher than that in the first step is applied to the electrode of the electrostatic chuck in the second step where a relatively high substrate temperature is required, the plasma generated in the vacuum chamber Without changing the state, only the temperature of the substrate can be changed in two stages. Therefore, since it is possible to change only the temperature of the substrate regardless of the amount of heat supplied from the plasma to the substrate, it is related to the temperature of the substrate from various conditions such as pressure in the first step and the second step. It is possible to remove the constraints. As a result, the degree of freedom of various conditions in the first step and the second step can be expanded, and the embedding property of the metal material can be further improved.

According to a third aspect of the present invention, there is provided an interior of a concave portion of a substrate disposed in the vacuum chamber by sputtering a metal target provided in the vacuum chamber with ions in plasma generated in the vacuum chamber. In a sputtering apparatus for embedding a metal material in the pressure chamber, a pressure adjusting unit that adjusts the pressure in the vacuum chamber, a bias power source that applies a bias voltage to the substrate, a temperature adjusting unit that adjusts the temperature of the substrate, and these pressure adjustments A control unit for controlling a driving mode of the unit, a bias power source, and a temperature control unit, wherein the control unit is configured to cause the metal particles emitted from the metal target to collide with charged particles in the plasma. By adjusting the pressure in the tank, charged metal particles are generated, and the charged metal particles are drawn onto the substrate so as to be drawn into the recesses. After performing the first step of applying astigmatism voltage, in a state of not applying the bias voltage, thereby lowering the pressure in the vacuum chamber, so that the metal particles adhering to the substrate to flow into the recess The second step of increasing the temperature of the substrate is performed, the metal target is a target containing aluminum, the distance between the metal target and the substrate is 30 mm or more and 90 mm or less, and the control unit When performing the first step, a bias voltage is applied to the substrate by supplying high frequency power having a frequency of 13.56 MHz to the substrate, and the pressure in the vacuum chamber is 5 Pa or more and 50 Pa or less, temperature of the substrate is less than or equal to and 200 ° C. 20 ° C. or higher, the high frequency power is 7 × ¹⁰ -4 W / mm ² or more and 7 × ¹⁰ -3 W / mm Or less, when the control unit executes the second step, the pressure in the vacuum chamber is less and 0.5Pa above 0.01 Pa, the temperature of the substrate is 350 ° C. or higher and at 450 ° C. or less and the gist that there.

  According to the sputtering apparatus of the present invention, the sputtered metal particles first collide with the charged particles in the plasma to become charged metal particles. Although the metal particles lose directivity due to multiple scattering in the plasma, the metal particles fly toward the inside of the recesses provided in the substrate by the bias voltage applied to the substrate. As a result, the metal particles easily reach the bottom of the recess provided in the substrate, and the coverage of the metal particles on the inner surface of the recess is improved in the initial stage of film formation. Next, since the film formation is continued in a state where no bias voltage is applied to the substrate, so-called reverse sputtering in which ions in the plasma are attracted by the bias voltage and sputter metal particles attached to the substrate is suppressed. As a result, the film formation rate after the initial film is formed is higher than the film formation rate when the initial film is formed.

  And since the temperature of the substrate at the time of forming the initial film is lower than the temperature of the substrate after the formation of the initial film, the particle size of the metal particles adhering in the recesses is an initial film and a film laminated on the initial film. Become different from each other. In addition, since the temperature of the substrate after the formation of the initial film is a temperature at which the metal particles flow into the recesses, the grain size of the crystal grains in the initial film formed in the recesses is It becomes smaller than the grain size of the crystal grains. As a result, the fluidity of the metal particles in the film stacked on the initial film is promoted at the interface between the initial film and the film stacked on the initial film, and the metal material is easily embedded in the recess.

Thus, according to the sputtering apparatus of the present invention, when a metal material is embedded in the recess using a single sputtering apparatus, it is possible to improve the embedding property of the metal material.
Moreover, according to this invention, the distance of the target and board | substrate which is a flight distance of a metal particle is 30 mm or more and 90 mm or less, and the pressure in a 1st process is 5 Pa or more and 50 Pa or less. The collision frequency between the metal particles emitted from the target and the charged particles in the plasma increases as the distance between the target and the substrate increases and the pressure in the vacuum chamber increases. In addition, the charged metal particles are more easily attracted by the bias voltage applied to the substrate as the distance between the target and the substrate becomes shorter. In this regard, in the above sputtering method, the pressure in the vacuum chamber, the distance between the target and the substrate, and the supply amount of the high frequency power in the first step are set in the above range, so that the discharged metal Collisions between particles and charged particles and entrainment of charged metal particles occur more reliably.
The distance between the target and the substrate, which is the flight distance of the metal particles, is 30 mm or more and 90 mm or less, and the pressure in the vacuum chamber in the second step is 0.01 Pa or more and 0.5 Pa or less. The frequency of arrival of the metal particles emitted from the target to the surface of the substrate becomes so high that the metal particles emitted from the target are not scattered by the gas staying in the vacuum chamber. In this respect, in the sputtering method, the number of collisions between the sputtered particles and the various particles in the vacuum chamber can be suppressed and the film formation rate can be improved while securing the number of particles to be sputtered by the target.
In addition, since the temperature of the substrate in the first step is 20 ° C. or higher and 200 ° C. or lower, the increase in the particle diameter of the aluminum-containing film formed in the first step is suppressed. Further, since the temperature of the substrate in the second step is 350 ° C. or higher and 450 ° C. or lower, the fluidity of the aluminum-containing film formed in the second step can be surely expressed.

The schematic block diagram which shows schematic structure of the sputtering device concerning one embodiment of this invention. The figure which shows the relationship between the drive aspect of the chuck power supply provided in the sputtering device, and chuck voltage. (A) The conceptual diagram which shows notionally the behavior of the metal particle in the film-forming process in a high-pressure atmosphere, (b) The conceptual diagram which shows notionally the behavior of the metal particle in the film-forming process in a low-pressure atmosphere. (A)-(g) The timing chart which shows the timing of various operation | movement in the film-forming process using the sputtering method of this Embodiment, and its effect | action. (A) The conceptual diagram which shows notionally the film growth in the film-forming process in a high pressure atmosphere, (b) The conceptual diagram which shows notionally the film growth in the film-forming process in a low-pressure atmosphere.

  Hereinafter, an embodiment in which a sputtering method of the present invention and a sputtering apparatus for performing the sputtering method are embodied will be described with reference to FIGS. FIG. 1 shows a schematic configuration of the sputtering apparatus.

  A film forming space 11a for forming a film on the substrate S to be processed is formed inside the vacuum chamber 11 of the sputtering apparatus. A mass flow controller MFC that adjusts the flow rate of a sputtering gas such as argon (Ar) gas is connected to the vacuum chamber 11 via a supply pipe 12. From the mass flow controller MFC, argon gas is supplied into the film forming space 11a at a flow rate within a predetermined range. Note that the sputtering gas is not limited to argon gas, and a rare gas element gas such as neon (Ne) gas, krypton (Kr), or xenon (Xe) gas can be used.

  An exhaust unit PU having a turbo molecular pump, a dry pump, or the like is connected to the vacuum chamber 11 via an exhaust pipe 13. The pressure in the film formation space 11a is determined by the flow rate per unit time of the gas supplied to the film formation space 11a by the mass flow controller MFC and the exhaust speed of the exhaust unit PU. In the present embodiment, the pressure in the film formation space 11a is adjusted to a predetermined value by maintaining the exhaust speed of the exhaust unit PU constant and changing the flow rate of the gas supplied by the mass flow controller MFC. . In the present embodiment, for example, the mass flow controller MFC, the supply pipe 12, the exhaust part PU, and the exhaust pipe 13 constitute a pressure adjusting part.

  In the film forming space 11 a inside the vacuum chamber 11, a substrate stage 14 is provided on which the substrate S is placed and the position of the substrate S is fixed. Inside the substrate stage 14, a heater 15 that constitutes the placement surface of the substrate S is provided. The heater 15 is connected to a heater control unit HC that controls the current value supplied to the heater 15 and adjusts the temperature of the heater 15. The heater 15 heats the substrate S placed thereon to adjust the temperature of the substrate S to a predetermined range. In this Embodiment, the heater 15 comprises a temperature control part as a temperature control part, for example.

  The heater 15 is formed with a plurality of recesses 15a that open to the surface on which the substrate S is placed, and a temperature control gas flow path 15b that connects the recesses 15a and the temperature control gas controller TC. A temperature control gas such as helium gas is supplied from the temperature control gas control unit TC to the recess 15a through the temperature control gas channel 15b at a predetermined flow rate. The temperature control gas supplied to the recess 15 a becomes a heat medium generated by the heater 15 and efficiently transfers the heat of the heater 15 to the substrate S placed on the heater 15. In addition, as temperature control gas mentioned above, not only the above-mentioned helium gas but inert gas, such as argon gas and nitrogen gas, can be used, for example.

A high frequency power supply G1 for bias is connected to the substrate stage 14. A chuck power supply G <b> 2 is connected to the chuck electrode 16 provided in the heater 15.
The high frequency power supply G1 for bias supplies predetermined high frequency power to the substrate stage 14. When high frequency power is supplied to the substrate stage 14 from the bias high frequency power supply G1, a negative bias voltage is applied to the substrate S. The chuck power supply G <b> 2 applies a predetermined DC voltage for adsorbing the substrate S to the heater 15 to the chuck electrode 16. When a DC voltage is applied to the chuck electrode 16 from the chuck power supply G2, an electrostatic force corresponding to the DC voltage is generated between the substrate S and the heater 15, and the substrate S is electrostatically attracted to the heater 15. . In the present embodiment, the substrate stage 14, the heater 15, the chuck electrode 16, and the chuck power source G2 constitute an electrostatic chuck that heats the substrate S while electrostatically attracting it.

  Above the substrate stage 14, a cylindrical deposition preventing plate 17 is disposed over substantially the entire circumferential direction of the substrate S. The deposition preventing plate 17 suppresses adhesion of sputtered particles to the inner wall of the vacuum chamber 11 when the film forming process is performed in the film forming space 11a.

Directly above the substrate stage 14 and above the deposition preventing plate 17, a target 18 formed in a disk shape with an aluminum-copper alloy (Al—Cu) as a main component is disposed. A target electrode 19 connected to the target power supply G3 is attached to the target 18. The target electrode 19 is a vacuum chamber in which the sputtering surface of the target 18 and the deposition surface of the substrate S are opposed to each other, and the TS distance _DTS, which is the distance between the target 18 and the substrate S, is a predetermined distance. 11 is fixed.

  A magnetic circuit 21 that forms a magnetron magnetic field along the surface to be sputtered of the target 18 is disposed above the target electrode 19. When a predetermined DC voltage is applied to the target electrode 19 from the target power supply G3, the sputtering gas supplied into the film formation space 11a is turned into plasma near the surface to be sputtered of the target 18. Furthermore, the magnetron magnetic field formed by the magnetic circuit 21 increases the plasma density in the vicinity of the surface to be sputtered of the target 18.

  The sputter apparatus has a main control in which various power sources including a bias high-frequency power source G1, a chuck power source G2, and a target power source G3 and various control units such as a heater control unit HC and a temperature control gas control unit TC are electrically connected. A portion 22 is provided. The main control unit 22 gives various commands (commands) for controlling their driving modes to various power sources and various control units. The storage unit 23 included in the main control unit 22 stores various power sources, a table in which driving modes of various control units and commands are associated with each other.

  In the sputtering apparatus, when the substrate S is carried into the film formation space 11a with the heater 15 heated to a predetermined temperature, a predetermined flow rate of argon gas is supplied to the film formation space 11a. Next, a predetermined DC voltage is applied to the chuck electrode 16 from the chuck power supply G 2, and the substrate S is electrostatically attracted to the substrate stage 14. Thereafter, a predetermined voltage is applied to the target 18 from the target power supply G3 to generate plasma made of argon gas, and the surface to be sputtered of the target 18 is sputtered by argon ions in the plasma.

In the present embodiment, the processing target of the sputtering apparatus is the substrate S having a recess formed in the insulating film, and the sputtering apparatus recesses the wiring made of Al—Cu through the film forming process in the film forming space 11a. Form in. The film forming process executed by the main controller 22 includes a first step of sputtering the target 18 while applying a bias voltage to the substrate S, and a second step of sputtering the target 18 without applying a bias voltage to the substrate S. Process. The main control unit 22 executes the first process and the second process in order. In the first step, the pressure in the vacuum chamber 11 is set so that the sputtered particles released by sputtering of the target 18 collide with argon ions having a positive charge. In the second step, the pressure in the vacuum chamber 11 is set lower than the pressure in the first step so that the collision between the sputtered particles and the argon ions does not occur. In the second step, the temperature of the substrate S is set higher than the temperature of the substrate S in the first step. In the film formation process, a predetermined current is supplied from the heater control unit HC to the heater 15 and the temperature of the heater 15 is maintained at 400 ° C. over the first step and the second step. The temperature of the substrate S is controlled by an electrostatic adsorption force acting between the substrate S and the heater 15.

  A method for adjusting the substrate temperature in the first step and the second step will be described with reference to FIG. FIG. 2 shows a table in which a chuck command, which is a command output to the chuck power supply G2 by the main control unit 22 provided in the sputtering apparatus, is associated with a chuck voltage applied to the chuck electrode 16 by the chuck power supply G2.

  There are three types of chuck commands, “OFF”, “ON1”, and “ON2”. When the main control unit 22 selects the chuck command “OFF” and outputs it to the chuck power supply G2, the chuck power supply G2 sets the chuck voltage applied to the chuck electrode 16 to 0V. When the main control unit 22 selects the chuck command “ON1” and outputs it to the chuck power supply G2, the chuck power supply G2 sets the chuck voltage applied to the chuck electrode 16 to 100 V (first DC voltage). When the main controller 22 selects the chuck command “ON2” and outputs it to the chuck power supply G2, the chuck power supply G2 sets the chuck voltage applied to the chuck electrode 16 to 800 V (second DC voltage).

  When the chuck voltage is set to 0 V, an electrostatic attracting force is not developed between the substrate S and the heater 15, and the substrate S is not attracted to the substrate stage 14. When the chuck voltage is set to 100 V and 800 V, an electrostatic attracting force appears between the substrate S and the heater 15, and the substrate S is attracted to the substrate stage 14. When the chuck voltage is set to 100V, compared with the case where the chuck voltage is set to 800V, the adsorption force between the substrate S and the heater 15 becomes weak, and heat is hardly transmitted from the heater 15 to the substrate S. . Therefore, when the chuck voltage is set to 100V, the substrate temperature becomes lower than when the chuck voltage is set to 800V.

  In the present embodiment, the chuck command “OFF” is selected by the main control unit 22 when the film forming process is not performed and when the film forming process is completed. When the first step is performed, the chuck command “ON1” is selected by the main control unit 22 and the temperature of the substrate S is maintained at 200 ° C. or lower. Then, when the second step is performed, the chuck command “ON2” is selected by the main control unit 22, and the temperature of the substrate S is maintained at 350 ° C. or more and 450 ° C. or less.

  According to such a configuration, the temperature of the substrate S is changed by the chuck voltage applied to the chuck electrode 16, so that the state of the plasma generated in the vacuum chamber 11 can be changed without changing the state of the plasma of the substrate S. Only the temperature can be changed in stages. Since only the temperature of the substrate S can be changed regardless of the amount of heat supplied from the plasma to the substrate S, the temperature of the substrate S can be determined from various conditions such as pressure in the first step and the second step. It is possible to remove the restrictions related to.

Here, it is known that the constituent particles of the Al—Cu film formed on the substrate S by the film formation process depend on the substrate temperature at the time of film formation. Specifically, the lower the temperature of the substrate S during film formation, the smaller the particle size of the particles constituting the Al—Cu film, and the higher the temperature of the substrate S, the particle size of the particles constituting the Al—Cu film. Will grow. Therefore, in this embodiment, the particle size of the particles constituting the Al—Cu film formed in the second step is larger than the particle size of the particles constituting the Al—Cu film formed in the first step. Will be bigger.

Next, the action of the pressure in the vacuum chamber 11 during the film forming process on the trajectory of the metal particles as the sputter particles and the film forming speed of the metal film will be described with reference to FIG. 3 (a) is the behavior of the metal particles when carrying out the deposition process in the vacuum chamber 11 as the atmosphere of a high pressure P _H is schematically shown, FIG. 3 (b), a vacuum chamber 11 the behavior of metal particles when carrying out the film forming process as the atmosphere of the low pressure P _L conceptually shows. Note that a bias voltage is applied to the substrate S in the high-pressure atmosphere film forming process shown in FIG. As described above, in the present embodiment, the pressure in the vacuum chamber 11 is adjusted by changing the flow rate per unit time of the argon gas supplied into the vacuum chamber 11 through the supply pipe 12. Yes.

As shown in FIG. 3 (a), when carrying out the film forming process for applying a voltage of, for example, more than 10kW the target 18 as a condition of the high pressure _{P H} and the following 50Pa or more 5Pa the pressure in the vacuum chamber 11, the deposition Argon gas is excited and becomes positive ions in a region A near the target 18 in the space 11a. Argon which has become positive ions in the region A sputters the surface to be sputtered of the target 18, and metal particles MP made of Al, Cu, or an alloy of Al and Cu are released.

Since the pressure in the vacuum chamber 11 is pressure P _H, the released metal particles MP is in the region B of the substrate S side of the region A or the region A in the film forming space 11a, it is a positive charged particles IP Collides with argon ions one or more times. As a result, charge exchange occurs between the neutral metal particle MP and the positive charged particle IP. Incidentally, TS distance _{D TS} to 30~90mm a distance between the target 18 and the substrate S, when less and 50Pa or more 5Pa the pressure in the vacuum chamber 11, the average number of collisions between the metal particles MP and the charged particles IP is Hundreds of times. That is, the high pressure P _H in the present embodiment, a reference pressure P _TH or more pressure the average number of collisions between the metal particles MP and the charged particles IP is one.

When the metal particles MP having a positive charge reach the region C in the vicinity of the substrate S, the metal particles MP are attracted to the film formation surface of the substrate S by the negative bias voltage applied to the substrate S. Therefore, when carrying out the deposition process the pressure in the vacuum chamber 11 as a high pressure P _H, the metal particles MP released from the sputtered surface of the target 18, the in directivity, in particular substrate S relative to that of the flight direction Directivity along the normal direction of the film formation surface is given.

On the other hand, as shown in FIG. 3 (b), is applied, for example 10kW or more voltage to the target 18, the deposition condition of the low pressure _{P L} and less 0.5Pa or 0.01Pa the pressure in the vacuum chamber 11 When the treatment is performed, argon becomes positive ions in the region A. Then, the positive ions of argon sputter the surface to be sputtered of the target 18 to release metal particles MP made of Al, Cu, or an alloy of Al and Cu.

Most of the released metal particles MP do not collide with the positive charged particles IP in the region B of the region A on the substrate S side, and the metal particles MP are maintained in a neutral state. Land on the deposition surface. At this time, since a bias voltage is not applied to the substrate S, most of the metal particles MP emitted from the surface to be sputtered of the target 18 fly in the region B while maintaining the distribution of the emission angle, and the substrate S is covered. Land on the deposition surface. Note that the TS distance _{D TS} is the distance between the target 18 and the substrate S 30～90Mm, when less and 0.5Pa or 0.01Pa the pressure in the vacuum chamber 11, the metal particles MP and the charged particles IP The average number of collisions is one. That is, the low pressure P _L in this embodiment is a pressure lower than the reference pressure P _TH average number of collisions between the metal particles MP and the charged particles IP is one.

Here, when the voltage applied to the target 18 is constant, the pressure in the vacuum chamber 11 and the film formation speed on the film formation surface of the substrate S are the following (i) to ( It has a different relationship depending on the range of iii).

  (I) When the number of argon particles in the vacuum chamber 11 is insufficient with respect to the voltage applied to the target 18, the deposition rate increases as the number of argon particles, that is, the pressure in the vacuum chamber 11 increases.

  (Ii) When the number of argon particles in the vacuum chamber 11 is not excessive or insufficient with respect to the voltage applied to the target 18, the deposition rate is substantially constant regardless of the number of argon particles, that is, the pressure in the vacuum chamber 11. Maintained.

  (Iii) When the number of argon particles in the vacuum chamber 11 exceeds a range in which the voltage applied to the target 18 is not excessive or insufficient, the deposition rate decreases as the number of argon particles, that is, the pressure in the vacuum chamber 11 increases. Become.

In this embodiment, the pressure in the vacuum chamber 11 in the first step is high P _H contained in a pressure range of (iii), the pressure in the vacuum chamber 11 in the second step is (ii) a low pressure P _L that is included in the pressure range. Therefore, in the first step, although the metal particles MP can easily reach the bottom of the concave portion of the substrate S, the film formation rate is lowered. On the other hand, in the second step, a higher deposition rate can be obtained as compared with the first step in order to compensate for the decrease in the deposition rate in the first step.

  A driving mode and an operation of the sputtering apparatus when the film forming process using the sputtering method of the present embodiment is performed will be described with reference to FIGS. FIG. 4 shows (a) a mass flow controller MFC and (b) (c) (d) various power source driving modes and (e) a pressure in the vacuum chamber 11 when a film forming process is performed. , (F) the temperature of the substrate S, and (g) the timing of the change in the pressure of the argon gas supplied to the back surface of the substrate S. FIG. 5 conceptually shows the growth process of the metal film in each step, FIG. 5 (a) shows the growth process of the metal film in the first step, and FIG. 5 (b) shows the metal film in the second step. Each shows the growth process.

As shown in FIG. 4, when the substrate S is carried into the film formation space 11 a, for example, 3 to 3 from the mass flow controller MFC into the film formation space 11 a at the timing t <b> 1 when the first process starts. Argon gas is supplied at a flow rate F2 of 500 sccm (FIG. 4A). Thereby, the film forming pressure becomes a pressure P _H , for example, 5 Pa or more and 50 Pa or less (FIG. 4E).

  Next, the chuck command “ON1” is selected in the main control unit 22, and a chuck voltage V1 of, for example, 100 V is applied from the chuck power supply G2 to the chuck electrode 16 (FIG. 4D). Thereby, the substrate S is electrostatically attracted to the substrate stage 14, and the temperature of the substrate S is maintained at a temperature T1, for example, 200 ° C. or less (FIG. 4F).

  Subsequently, a target voltage Vt, for example, a voltage of 10 kW or more is applied to the target 18 from the target power supply G3. As a result, plasma made of argon gas is generated, and the surface to be sputtered of the target 18 is sputtered by argon ions to release the metal particles MP (FIG. 4B).

When plasma is generated in the film formation space 11a, the high frequency power supply G1 for bias supplies the chuck electrode 16 with an electric energy Vb, for example, 7 × 10 ⁻⁴ W / mm ² or more and 7 × 10 ⁻³ W / mm ² or less. Supply high frequency power. As a result, a negative bias voltage is applied to the substrate S (
FIG. 4 (c)). In the first process, since argon gas is not supplied to the back surface of the substrate S, its pressure _PAr is set to zero.

In short, in the first step,
Pressure inside the vacuum chamber 11 is equal to or higher than the reference voltage _{P TH} pressure _{P H}
・ High frequency power supply G1 for bias is “ON”
・ "ON1" as the chuck command
The film forming process is performed under the conditions where these are selected.

According to this, as shown in FIG. 5A, the metal particles MP emitted from the surface to be sputtered of the target 18 are charged by collision with the argon ions as charged particles and applied to the substrate S. The directivity toward the bottom of the recess H is obtained by the action of the bias voltage. Therefore, the liner layer L _L which is an Al—Cu alloy thin film is formed not only on the side wall of the recess H but also on the bottom thereof. At this time, since the temperature of the substrate S is a 200 ° C. or less, the particle diameter of the particles of the Al-Cu alloy constituting the liner layer L _L, the growth is suppressed.

When a predetermined time has elapsed from the start of the first process, the second process is started at timing t2. At the start of the second step, first, the bias high-frequency power supply G1 stops the supply of high-frequency power to the chuck electrode 16 (FIG. 4C). As described above, in the second step, the bias high-frequency power source G1 is turned “OFF” at the start thereof, so that argon ions are drawn into the liner layer L _L formed in the first step. The occurrence of reverse sputtering can be suppressed. Therefore, it is possible to suppress the liner layer L _{L from} being scraped by reverse sputtering.

Next, argon gas is supplied from the mass flow controller MFC to the film formation space 11a at a flow rate F1 lower than the flow rate F2, for example, 20 to 100 sccm (FIG. 4A). By adjusting the flow rate and the exhaust system of an argon gas, film formation pressure is the reference pressure _{P TH} higher pressure _{P H} than reference pressure _{P TH} pressure lower than _{P L,} for example 0.01Pa and not more than 0.5Pa below It is changed (FIG. 4 (e)). Then, the voltage applied to the chuck electrode 16 from the chuck power supply G2 is changed from the chuck voltage V1 to the chuck voltage V2, for example, 800V. That is, “ON2” is selected as the chuck command by the main control unit 22. Thereby, the contact area between the substrate S and the heater 15 is increased, the efficiency of transfer of heat generated from the heater 15 is increased, and the temperature of the substrate S is changed from the temperature T1 to the temperature T2, for example, 350 ° C. or more and 450 ° C. or less. It rises (FIG. 4 (f)). At this time, in order to further enhance the conduction of heat to the substrate S, argon gas is supplied to the back surface of the substrate S from the temperature control gas control unit TC at a pressure P _Ar , for example, 400 Pa (FIG. 4G). .

In short, in the second step,
・ Low pressure P _L where the pressure in the vacuum chamber 11 is lower than the reference pressure P _TH
・ High frequency power supply G1 for bias is “OFF”
・ "ON2" as the chuck command
The film forming process is performed under the conditions where these are selected.

According to this, as shown in FIG. 5B, the metal particles MP emitted from the surface to be sputtered of the target 18 hardly collide with other particles in the film formation space 11a, and the distribution of the emission angles. And landing on the substrate S. Therefore, the metal particles MP is a directivity of granted flight direction upon release reach the substrate S, to form a bulk layer L _B. In addition, since the metal particles MP are highly likely to land on the substrate S without being scattered by charged particles or the like, the deposition rate on the substrate S is maintained high. At this time, since the temperature of the substrate S is set to 350 ° C. or higher and 450 ° C. or less, the particles of A-Cu alloy constituting the bulk layer L _B constitutes the liner layer L _L formed in the first step It grows to a particle size larger than that of the Al—Cu alloy particles. As a result, the boundary between the liner layer L _L and the bulk layer L _B, by cooperating with the hot conditions, the bulk layer L _B comes to have fluidity. And will be Al-Cu alloy film is introduced into the recess H by the flow of the bulk layer L _B, so that the recess H is filled with Al-Cu alloy film.
[Example]
Using a sputtering method comprising first and second steps in which the pressure in the vacuum chamber and the substrate temperature are different, a film forming process for embedding a via plug in a via hole as a recess formed in the substrate was performed. And the cross-sectional image in the via hole after the 1st and 2nd process and the cross-sectional image in the via hole after the 1st process were imaged with the scanning electron microscope, and the embedding property of each process was evaluated. Note that an Al—Cu alloy was used as a target of the sputtering apparatus.

・ Shape of via hole Opening diameter 136nm
Bottom diameter 136nm
Length between opening and bottom (depth of via hole) 286 nm
Aspect ratio 2.1
・ TS distance 45mm
・ Target voltage (DC) 14kW
・ Pressure inside the vacuum chamber (Argon gas supply flow rate)
First step 20Pa (55sccm)
Second step 0.12 Pa (30 sccm)
・ Bias voltage (standard value)
1st process 200W (0.003W / mm < ² >)
Second step 0W
・ Thickness liner layer 200nm
Bulk layer 500nm
According to the above conditions, it was found that the via hole was completely filled with the Al—Cu alloy. In addition, the thickness of the via hole bottom surface of the liner layer formed in the first step was measured as Tb, the thickness Td of the via hole side surface, and the film thickness To outside the opening. As a result, the coverage ratio of the via hole bottom surface (Tb / To × 100 ) Was 39.5%, and the via hole side coverage (Ts / To × 100) was 19%. And in the film-forming process using the sputtering method described in this embodiment, if the various conditions described in the embodiment are satisfied, the coverage of the inner surface of the recess by the liner layer is maintained high. I found out that it would be. It has also been found that if the various conditions described in the embodiment are satisfied, the embedding property of the recess is maintained high by the liner layer and the bulk layer.

As described above, according to the present embodiment, the effects listed below can be obtained.
(1) In the first step, to generate the metal particles MP which a charged particle IP in the released metal particles MP and plasma were charged to sputter the target 18 by the pressure P _H of collision from the target 18, The charged metal particles MP were drawn toward the inside of the recess by a bias voltage. Thereby, in the first step, the sputtered metal particles MP collide with the charged particles IP in the plasma to become charged metal particles MP. The metal particles MP that reach the region C in the vicinity of the substrate S lose directivity due to multiple scattering in the plasma, but the bias voltage applied to the substrate S causes the metal particles MP to enter the recesses provided in the substrate S. To fly towards. As a result, the metal particles MP can easily reach the bottom of the concave portion provided in the substrate S, and the coverage of the metal particles MP on the inner surface of the concave portion is improved.

  (2) In the second step, film formation is performed in a state where no bias voltage is applied to the substrate S. Therefore, so-called reverse sputtering in which argon ions in the plasma are attracted by the bias voltage and sputter the metal particles MP attached to the substrate S can be suppressed.

  (3) The temperature T1 of the substrate S in the first step is set lower than the temperature T2 of the substrate S in the second step. As a result, the particle diameters of the metal particles MP adhering in the recesses are different from each other in the first step and the second step. In addition, the temperature of the substrate in the second step was set higher than the temperature of the substrate in the first step so that the metal particles flow into the recesses. As a result, the fluidity of the metal particles adhered in the second step is promoted at the interface between the metal film formed in the first step and the metal film formed in the second step, so that It becomes easy to embed a metal material in. That is, when a metal material is embedded in the recess using a single sputtering apparatus, the embedding property of the metal material can be improved.

  (4) Since the pressure in the vacuum chamber 11 in the second step is lower than that in the first step, the collision frequency between the sputtered metal particles MP and other particles is lower than in the first step. Become. As a result, since the sputtered metal particles MP are less likely to be scattered, the number of metal particles MP that reach the substrate S per unit time increases, and the film formation rate becomes higher than in the first step. In the second step, the embeddability is ensured by the fluidity imparted to the metal particles MP. Therefore, the processing speed can be increased while maintaining the embeddability by the increase in the film formation rate of the second step. It becomes possible.

  (5) The temperature of the substrate S is changed by the chuck voltage applied to the chuck electrode 16. Thereby, only the temperature of the substrate S can be changed in two stages without changing the state of the plasma generated in the vacuum chamber 11. Therefore, since it is possible to change only the temperature of the substrate S regardless of the amount of heat supplied from the plasma to the substrate S, the substrate S can be changed from various conditions such as pressure in the first step and the second step. It is possible to remove the constraints related to temperature. As a result, the degree of freedom of various conditions in the first step and the second step can be expanded, and the embedding property of the metal material can be further improved.

(4) The TS distance _DTS, which is the flight distance of the metal particles MP, is 30 mm or more and 90 mm or less, the pressure in the first step is 5 Pa or more and 50 Pa or less, and the high frequency power is 7 × 10 ^−4. W / mm ² or more and 7 × 10 ⁻³ W / mm ² or less. Thereby, the collision between the released metal particles MP and the charged particles IP and the drawing of the charged metal particles can be caused more reliably.

  (5) The TS distance, which is the flight distance of the metal particles MP, was set to 30 mm to 90 mm, and the pressure in the vacuum chamber 11 in the second step was set to 0.01 Pa to 0.5 Pa. Thereby, while ensuring the number of particles for sputtering the target 18, the number of collisions between the sputtered particles and various particles in the vacuum chamber 11 can be suppressed, and the film formation rate can be improved.

(6) The temperature of the substrate S in the first step was set to 20 ° C. or more and 200 ° C. or less. Thereby, the expansion of the particle size of the metal particles in the Al—Cu alloy film formed in the first step is suppressed.
(7) The temperature of the substrate S in the second step was set to 350 ° C. or higher and 450 ° C. or lower. Thereby, the fluidity of the Al—Cu alloy film formed in the second step can be surely exhibited.

In addition, the said embodiment can also be suitably changed and implemented as follows.
The chuck command is not limited to three types of “OFF”, “ON1”, and “ON2”, and may be configured to set four or more types. Further, the value of the chuck voltage set by the chuck command can be arbitrarily changed.

  In the second step, argon gas is supplied to the back surface of the substrate S. However, the present invention is not limited to this, and a configuration in which argon gas is not supplied may be used as long as the temperature of the substrate S is sufficiently increased by an electrostatic adsorption force. Further, if fluidity is imparted to the crystal grains in the metal film formed in the second step, argon gas is supplied to the back surface of the substrate S in both the first step and the second step. It may be configured.

  -The structure which adjusts the pressure in the vacuum chamber 11 by changing the exhaust capability of an exhaust part, maintaining the supply flow rate of the argon gas supplied to the vacuum chamber 11 may be sufficient. Moreover, the structure which adjusts the pressure in the vacuum chamber 11 by changing the supply flow rate of the argon gas supplied to the vacuum chamber 11, and the exhaust_gas | exhaustion capacity of an exhaust_gas | exhaustion part may be sufficient.

  The above-described sputtering apparatus can be embodied in an apparatus that does not include the magnetic circuit 21, and the above-described sputtering method can be executed using an apparatus having such a configuration.

  The high frequency power supply destination for applying the bias voltage to the substrate S is different from the chuck voltage application destination for electrostatically adsorbing the substrate S. By changing this, the supply destination of the high-frequency power and the application destination of the chuck voltage for electrostatically attracting the substrate S may be a single electrode. A configuration may be employed in which the electrode serving as the supply destination of the high frequency power and the electrode serving as the application destination of the DC voltage are separately provided in the substrate stage 14.

The reference pressure _PTH for determining the film formation pressure in the first step and the second step is not limited to the pressure at which the metal particle MP collides with the charged particle IP once, but the shape of the recess formed in the substrate S The pressure at which the metal particles MP collide with the charged particles IP n times (n ≧ 2) may be used. This is because the number of metal particles MP to be drawn by the bias voltage applied to the substrate S and the coverage of the inner surface of the recess differ depending on the shape of the recess.

  -An Al-Cu alloy film was formed using the target 18 which has an Al-Cu alloy as a main component. However, the present invention is not limited thereto, and a wiring made of a metal other than an aluminum Al—Cu alloy may be formed using a target mainly composed of another metal material.

  A configuration in which the temperature of the substrate S is changed by directly changing the temperature of the heater 15 while maintaining the chuck voltage may be used. Further, the temperature of the substrate S may be changed by changing the chuck voltage and the output of the heater 15.

DESCRIPTION OF SYMBOLS 11 ... Vacuum chamber, 11a ... Deposition space, 12 ... Supply piping, 13 ... Exhaust piping, 14 ... Substrate stage, 15 ... Heater, 15a ... Recess, 15b ... Temperature control gas flow path, 16 ... Chuck electrode, 17 ... Prevention Attaching plate, 18 ... target, 19 ... target electrode, 21 ... magnetic circuit, 22 ... main control unit, 23 ... storage unit, G1 ... bias high frequency power supply (bias power supply), G2 ... chuck power supply, G3 ... target power supply, H ... recess, HC ... heater control unit, L _B ... bulk layer, L _I ... insulating layer, L _L ... liner layer, MFC ... flow rate adjustment unit, PU ... exhaust unit, S ... substrate, TC ... temperature control gas control unit .

Claims (3)

In a sputtering method of embedding a metal material in a concave portion of a substrate disposed in the vacuum chamber by sputtering a metal target provided in the vacuum chamber with ions in plasma generated in the vacuum chamber,
A first step of sputtering the metal target while applying a bias voltage to the substrate;
A second step of sputtering the metal target without applying a bias voltage to the substrate in order in the vacuum chamber;
In the first step, the metal target is sputtered at a pressure at which the metal particles emitted from the metal target and the charged particles in the plasma collide to generate charged metal particles, and the charge is charged. The drawn metal particles are drawn into the recess by the bias voltage,
In the second step, the temperature of the substrate is set higher than that in the first step so that the metal particles adhering to the substrate flow into the recess, and the metal target is sputtered .
The metal target is a target comprising aluminum;
The distance between the metal target and the substrate is 30 mm or more and 90 mm or less,
In the first step,
A bias voltage is applied to the substrate by supplying high frequency power having a frequency of 13.56 MHz to the substrate;
The pressure in the vacuum chamber is 5 Pa or more and 50 Pa or less,
The temperature of the substrate is 20 ° C. or more and 200 ° C. or less,
The high-frequency power is 7 × 10 ⁻⁴ W / mm ² or more and 7 × 10 ⁻³ W / mm ² or less,
In the second step,
The pressure in the vacuum chamber is 0.01 Pa or more and 0.5 Pa or less,
The sputtering method, wherein a temperature of the substrate is 350 ° C. or higher and 450 ° C. or lower . The sputtering method according to claim 1 ,
An electrostatic chuck that is provided in the vacuum chamber and electrostatically adsorbs the substrate and heats the substrate with an amount of heat corresponding to the adsorption force,
In the first step, a first DC voltage is applied to the electrode of the electrostatic chuck.
In the second step, by applying a second DC voltage higher than the first DC voltage to the electrode of the electrostatic chuck, the temperature of the substrate is made higher than that in the first step.
A sputtering method characterized by the above. In a sputtering apparatus that embeds a metal material in a concave portion of a substrate disposed in the vacuum chamber by sputtering a metal target provided in the vacuum chamber with ions in plasma generated in the vacuum chamber,
A pressure adjusting unit for adjusting the pressure in the vacuum chamber;
A bias power source for applying a bias voltage to the substrate;
A temperature control unit for adjusting the temperature of the substrate;
These pressure adjustment unit, bias power source, and a control unit for controlling the driving mode of the temperature control unit,
The controller is
The charged metal particles are generated by adjusting the pressure in the vacuum chamber so that the metal particles emitted from the metal target and the charged particles in the plasma collide with each other. After performing the first step of applying the bias voltage to the substrate so as to draw particles into the recess,
In a state where the bias voltage is not applied, a second step is performed in which the pressure in the vacuum chamber is reduced and the temperature of the substrate is increased so that metal particles attached to the substrate flow into the recess. ,
The metal target is a target comprising aluminum;
The distance between the metal target and the substrate is 30 mm or more and 90 mm or less,
When the control unit executes the first step,
A bias voltage is applied to the substrate by supplying high frequency power having a frequency of 13.56 MHz to the substrate;
The pressure in the vacuum chamber is 5 Pa or more and 50 Pa or less,
The temperature of the substrate is 20 ° C. or more and 200 ° C. or less,
The high-frequency power is 7 × 10 ⁻⁴ W / mm ² or more and 7 × 10 ⁻³ W / mm ² or less,
When the control unit executes the second step,
The pressure in the vacuum chamber is 0.01 Pa or more and 0.5 Pa or less,
A sputtering apparatus, wherein the temperature of the substrate is 350 ° C. or higher and 450 ° C. or lower .

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