JP5661452B2 - Sputtering method - Google Patents

Description

  The present invention relates to a sputtering method used for depositing a material on a substrate in a manufacturing process of a semiconductor device or the like.

A sputtering apparatus for depositing a thin film on a substrate has a vacuum vessel evacuated to a vacuum. In general, a sputtering apparatus introduces an inert gas such as Ar into a vacuum vessel and applies a high voltage to a target to generate plasma. The target material is attached to the substrate supported by the substrate holder by utilizing the target sputtering phenomenon by charged particles in the discharge plasma.
When positive ions in the plasma are incident on a target material having a negative potential, atoms and molecules of the target material are blown off from the target material. This is called sputtered particles. The sputtered particles adhere to the substrate to form a film containing the target material.

  The gas introduced into the vacuum vessel is sputtered by adding a reactive gas such as nitrogen or oxygen to an inert gas such as Ar, thereby causing a reaction between the target material and the reactive gas. Thereby, an oxide or nitride of the target material is deposited. This is called reactive sputtering.

  When the target is discharged while introducing the reactive gas into the vacuum vessel, when the amount of the reactive gas introduced exceeds a certain threshold, the reactive gas atoms adhere to the target surface, and the state of the discharge plasma is Change. Along with this, the deposition rate on the substrate is greatly reduced. A state in which the reactive gas atoms adhere to the surface of the target and the film formation rate is slow is referred to as a poison mode. On the other hand, the state in which the reactive gas does not adhere to the target surface and the metal surface is exposed and the film forming speed is high is called a metal mode. The deposited film in which the reactive gas is sufficiently introduced and discharged in the poison mode is a stable compound.

  When at least two different types of targets are simultaneously discharged, the two or more different materials are simultaneously sputtered and deposited on the substrate to form these compounds.

  In Patent Document 1, a metal nitride (AlTiN) containing titanium and aluminum is prepared by simultaneously discharging a titanium target and an aluminum target, and simultaneously introducing an inert gas and a nitrogen gas into a vacuum chamber. Technology is disclosed. This AlTiN can be used as an electrode film for a metal gate.

JP 2000-038663 A

  However, in the above technique, nitriding proceeds on both the titanium target and the aluminum target by the nitrogen gas, and not only titanium nitride but also insulating aluminum nitride is formed. For this reason, the electric resistance of the deposited thin film becomes high, and the film is not suitable for a metal gate. Further, even when an alloy target of titanium and aluminum is used, the same result is obtained, and it is difficult to obtain a film for a metal gate.

  That is, in the conventional reactive sputtering by simultaneous discharge of a plurality of targets, it is very difficult to control the composition of the film deposited by reactive sputtering.

  On the other hand, AlTiN film formation in which the reaction between aluminum and nitrogen is suppressed by performing simultaneous sputtering using a titanium nitride target and an aluminum target is also conceivable. However, according to this method, it is necessary to replace the target every time the required film quality is changed.

In view of the above-described problems, an object of the present invention is to provide a sputtering method capable of forming a compound having a desired composition on a substrate in reactive sputtering by simultaneous discharge of a plurality of targets.

In order to solve the above-described problems, the present invention is configured such that an inert gas and a reactive gas are introduced into a vacuum vessel in which two target holders to which targets of different materials are attached are arranged. When the film containing the mixture of the materials of the two targets is formed on the substrate by applying a constant power to the target holder and simultaneously sputtering the two targets, The amount of the reactive gas that reacts with each of the two targets to generate a reaction product varies depending on the target, so that during sputtering, one of the two targets is in poison mode, The other is in metal mode and the substrate is a mixture of the two target materials Film for metal gate electrode containing is characterized in that it is deposited.

  According to the present invention, a compound having a desired composition can be formed on a substrate in reactive sputtering by simultaneous discharge of a plurality of targets.

It is a figure which shows the sputtering device which concerns on one Embodiment of this invention. It is a block diagram of the main control part for operating the sputtering device concerning one embodiment of the present invention. In reactive sputtering, (a) It is a figure which shows the relationship between the reactive gas flow rate and film-forming speed | velocity | rate when a reactive gas is uniformly introduce | transduced in a sputtering device. (B) It is a figure which shows the relationship between the reactive gas flow rate and the film-forming speed | velocity | rate at the time of introducing reactive gas from the target vicinity. It is a figure for demonstrating the conventional reactive sputtering method. It is a figure which shows the sputtering device concerning one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be variously modified without departing from the gist of the present invention. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

(First embodiment)
With reference to FIG. 1, an overall configuration of a sputtering apparatus (hereinafter also referred to as “film forming apparatus”) according to the present embodiment will be described. FIG. 1 is a schematic view of a film forming apparatus 1 according to this embodiment. The film forming apparatus 1 includes a vacuum container 2. The vacuum vessel 2 is connected to a vacuum exhaust device having a turbo molecular pump 48 and a dry pump 49 that exhaust the vacuum vessel 2 through an exhaust port 8. Further, the film forming apparatus 1 includes an inert gas introduction mechanism 17 that can introduce an inert gas into the vacuum vessel 2 and reactive gas introduction mechanisms 15 a and 15 b that can introduce a reactive gas. Yes.

  The exhaust port 8 is a conduit having a rectangular cross section, for example, and connects the vacuum vessel 2 and the turbo molecular pump 48. A main valve 47 is provided between the exhaust port 8 and the turbo molecular pump 48.

  Inside the vacuum vessel 2, targets 4 a and 4 b with exposed surfaces to be sputtered are held on a target holder 6 via a back plate 5. A substrate holder 7 for holding the substrate 10 is provided at a predetermined position where the sputtered particles emitted from the targets 4a and 4b reach. In addition, the vacuum vessel 2 is provided with a pressure gauge 41 for measuring the pressure of the vacuum vessel 2. A grounded cylindrical shield 40 (an adhesion shield member) is provided on the inner surface of the vacuum vessel 2. The shield 40 prevents sputtered particles from directly attaching to the inner surface of the vacuum vessel 2. In FIG. 1, the number of targets is two, but a larger number may be used. In FIG. 1, the reactive gas introduction mechanism is provided beside both targets, but the reactive gas introduction mechanism may be provided only in the vicinity of the target where reaction with the reactive gas is desired.

  The targets 4 a and 4 b are disposed obliquely above the substrate 10. The target holder 6 is connected to a power supply 12 for applying sputtering discharge power. The film forming apparatus 1 shown in FIG. 1 includes a DC power source, but is not limited to this, and may include, for example, an RF power source. When an RF power source is used, it is necessary to install a matching unit between the power source 12 and the target holder 6. A voltage is applied to the targets 4a and 4b by the power source 12 to form plasma, whereby sputtering is performed.

  The target holder 6 is insulated from the vacuum vessel 2 by an insulator. Since the target holder 6 is made of a metal such as Cu, it becomes an electrode when DC or RF power is applied. As is well known, the targets 4a and 4b are made of material components desired to be deposited on the substrate. Since it relates to the purity of the film, a high purity is desirable. The back plate 5 installed between the targets 4a and 4b and the target holder 6 is made of a metal such as Cu.

  In the vicinity of the target holder 6, a cylindrical adhesion preventing member 3 is installed so as to cover the target holder 6, thereby preventing sputter particles from directly adhering to the inner surface of the vacuum vessel 2.

  The inert gas introduction mechanism 17 cuts off or starts the supply of gas, a pipe for introducing the inert gas, a cylinder for storing the inert gas, a mass flow controller for controlling the flow rate of the inert gas, and the like. It consists of valves, pressure reducing valves, filters, etc. Further, the inert gas introduction mechanism 17 is configured to allow a designated gas flow rate to flow stably by the control device. The inert gas is introduced into the vacuum vessel 2 from the inert gas introduction unit 18.

  The reactive gas introduction mechanisms 15a and 15b include piping for introducing the reactive gas, a cylinder for storing the reactive gas, a mass flow controller for controlling the flow rate of the reactive gas, and shutting off or starting the gas flow. It consists of valves, a pressure reducing valve, a filter, etc. Further, the reactive gas introduction mechanisms 15a and 15b are configured to allow a designated gas flow rate to flow stably by the control device. The reactive gas is introduced into the vacuum vessel 2 from the reactive gas introduction portions 16a and 16b.

  In FIG. 1, the inert gas introduction part and the reactive gas introduction part are provided at different positions, but the inert gas and the reactive gas may be introduced into the vacuum vessel 2 from the same gas introduction part. .

  Next, a procedure of a film forming method using the film forming apparatus 1 according to the present embodiment will be described with reference to FIGS.

  The main control unit 100 of the film forming apparatus 1 according to the present embodiment includes, for example, a general computer and various drivers. That is, the main control unit 100 includes a CPU (not shown) that executes processing operations such as various calculations, controls, and determinations, and a ROM (not shown) that stores various control programs executed by the CPU. Have. The main control unit 100 also includes a RAM that temporarily stores data during the CPU processing operation, input data, and the like, and a non-volatile memory such as a flash memory and an SRAM (not shown). In such a configuration, the main control unit 100 executes the sputtering process in accordance with a predetermined program stored in the ROM or a command from the host device. Various process conditions such as discharge time, discharge power, and process pressure are controlled according to the command. Moreover, the output value of sensors, such as the pressure gauge 41 which measures the pressure inside the vacuum vessel 2, can also be acquired, and control according to the state of the apparatus is also possible.

  First, the main control unit 100 instructs the target shutter drive mechanism 14 to close the target shutter 13. In response to an instruction from the main controller 100, the target shutter 13 is closed. Next, the main control unit 100 instructs the control device that controls the inert gas introduction mechanism 17 to introduce the inert gas from the inert gas introduction mechanism 17 with the target shutter closed. For example, Ar is used as the inert gas. In addition, Ne, Kr, Xe, etc. are used. At the same time, the controller that controls the reactive gas introduction mechanisms 15a and 15b is instructed to introduce the reactive gas from the reactive gas introduction mechanisms 15a and 15b in the vicinity of the targets 4a and 4b. The amount of reactive gas introduced from the reactive gas introduction mechanisms 15a and 15b is adjusted depending on whether each target is sputtered in the poison mode or in the metal mode. The amount of reactive gas introduced may be set to 0 for the target to be sputtered in the metal mode. In this state, power is applied from the power source 12 to both the target 4a and the target 4b, and discharge is started.

  On the other hand, the main control unit 100 opens the gate valve 42 to instruct each control device to carry the substrate 10 to be processed into the vacuum vessel 2 and hold it in the substrate holder 7.

  Next, the main control unit 100 drives the target shutter drive mechanism 14 to instruct to open the target shutter 13. As a result, the sputtered particles that have jumped out of the target 4a and the target 4b adhere to the substrate 10, and a film is deposited. When the shield 40 is provided on the inner wall, sputtered particles adhere to the surface of the shield 40 and a film is deposited.

  After discharging for a predetermined time, the main control unit 100 stops the discharge by stopping the application of power to the power source 12. The main control unit 100 instructs the control device that controls the inert gas introduction mechanism 17 and the reactive gas introduction mechanisms 15a and 15b to stop the gas supply.

  By the above procedure, a compound having a desired composition can be formed while suppressing the reaction between the metal mode target and the reactive gas.

  Here, the effect when the reactive gas is introduced in the vicinity of the target will be described with reference to FIGS.

  FIG. 3A shows the relationship between the reactive gas flow rate and the film formation rate in normal reactive sputtering. The normal reactive sputtering means that the reactive gas is uniformly supplied to each target in the vacuum vessel 2 to perform sputtering of the target. As shown in FIG. 3A, when the reactive gas reaches a certain flow rate, the film forming speed decreases. This indicates that the target has changed from the metal mode to the poison mode.

  Next, FIG. 3B shows the relationship between the reactive gas flow rate and the deposition rate when a reactive gas introduction unit is connected near the target and the reactive gas is introduced near the target. As a comparative example, in FIG. 3B, the relationship between the reactive gas flow rate and the film formation rate in FIG. As can be seen from FIG. 3B, by introducing the reactive gas in the vicinity of the target, the threshold values of the metal mode and the poison mode with respect to the flow rate of the reactive gas can be changed. For this reason, it becomes possible to set it in the poison mode with a smaller reactive gas flow rate by introducing the reactive gas in the vicinity of the target for performing the film forming process as the poison mode. In this case, since the introduction amount of the reactive gas into the vacuum vessel 2 is reduced, it is possible to suppress the reaction between the target for performing the film forming process and the reactive gas in the metal mode.

  Further, if the positional relationship between each target and each reactive gas introduction part is the same, by adjusting the flow rate of the reactive gas introduced from each reactive gas introduction part into the vacuum vessel 2, Sputtering can be performed with the target in the poison mode and the other target in the metal mode.

  That is, the essence of the present invention is to control the reaction between each target and the reactive gas by controlling the supply amount of the reactive gas to each target in the simultaneous sputtering with two or more targets. It is to form a film of a compound having a composition.

  In the present invention, “the amount of gas introduced” refers to the absolute amount of gas introduced into the vacuum vessel 2. The “reactive gas supply amount to the target” refers to the amount of reactive gas that reacts with each target to generate a reaction product. Therefore, when 10 sccm of reactive gas is introduced into the vacuum vessel 2 and 1 sccm of the reactive gas reacts with the target, the “reactive gas supply amount to the target” is 1 sccm. Therefore, even if the amount of reactive gas introduced into each target is the same, the amount of reactive gas supplied to each target can be varied by changing the introduction position. Even if the positional relationship of the introduction positions is the same, the supply amount of the reactive gas to each target can be made different by changing the introduction amount of the reactive gas.

  An example in which this embodiment is applied to the formation of a metal gate electrode of a semiconductor device using the apparatus shown in FIG. 1 will be described below. In this embodiment, AlTiN is used as the metal gate electrode.

  As described in the problem related to the present invention, it is not preferable that AlN having high electric resistance is formed in AlTiN for metal gate. In this embodiment, the bonding of Al and N is suppressed, and AlTiN in which Ti and N are bonded is formed.

First, before film formation, discharge (conditioning discharge) for adjusting the condition is performed. Conditioning discharge was performed under the following conditions.
Inert gas: Ar gas Inert gas introduced amount: 20 sccm (standard cc / min)
Reactive gas: N2 gas Reactive gas introduction amount: 20 sccm
Pressure: 0.04Pa
Power supplied to each target: 700W
Conditioning time: 1200 seconds In the conditioning discharge, N2 gas, which is a reactive gas, was introduced only in the vicinity of the Ti target.

Thereafter, the substrate 10 in which SiO 2 (100 nm) is formed on the Si substrate having a diameter of 300 mm is placed on the substrate holder 7 of the film forming apparatus 1 to form a metal nitride film containing titanium and aluminum having a thickness of 10 nm. Went. The film forming conditions are shown below.
Inert gas: Ar gas Inert gas introduced amount: 20 sccm (standard cc / min)
Reactive gas: N2 gas Reactive gas introduction amount: 20 sccm
Pressure: 0.04Pa
Power supplied to each target: 700W
Sputtering time: 240 seconds At this time, N2 gas was introduced only in the vicinity of the Ti target in the same manner as the conditioning discharge.

  For comparison, another Si substrate having a diameter of 300 mm was carried in, and film formation was performed using the conventional film formation apparatus shown in FIG. 4 in which the nitrogen gas inlet was not near the titanium target but near the substrate. As the substrate, a substrate in which SiO 2 (100 nm) was formed on a 300 mm diameter Si substrate was used as in the above-described example. As shown in FIG. 4, in the conventional reactive sputtering method, the reactive gas is uniformly introduced into the film forming apparatus 1. A metal nitride film containing titanium and aluminum having a thickness of 10 nm was formed by the method shown in FIG. 4 using the same parameters as in this example.

  After the film formation of this example and the comparative example was completed, the specific resistance of the deposited film was measured in the range from the substrate center to the substrate edge of 5 mm using each sheet resistance measuring device (VR-120 manufactured by Hitachi Kokusai Electric Co., Ltd.). . From the measurement results, it was confirmed that the specific resistance of the deposited film was increased as compared with Example 1.

  Along with the specific resistance measurement, the deposited film created in Example 1 and the deposited film created in the comparative example were measured by XPS, and the bonding state of the atoms constituting the deposited film was confirmed. As a result, Al—N bonds were confirmed in the metal nitride containing titanium and aluminum formed by a conventional apparatus as a comparative example. On the other hand, Al—N bonds were hardly confirmed in the metal nitride containing titanium and aluminum formed by the sputtering method according to the present embodiment.

  From the above results, it was confirmed that when this embodiment is used, the bonding between aluminum and nitrogen is suppressed, and a metal nitride containing titanium and aluminum having a low specific resistance can be formed.

(Second Embodiment)
FIG. 5 shows a second embodiment different from the first embodiment. In this embodiment, the vacuum vessel 2 and the inert gas introduction mechanism are connected to positions different from those in the first embodiment. In this embodiment, the inert gas is introduced in the vicinity of the target that is set to the metal mode. By adopting such a configuration, a pressure gradient is formed in the vicinity of the target and in the space of the vacuum vessel 2. For this reason, it becomes possible to prevent the reactive gas diffused inside the vacuum vessel 2 from being mixed in the vicinity of the metal mode target. In addition to the target for the metal mode, an inert gas introduction part may be provided in the vicinity of the target for the poison mode.

DESCRIPTION OF SYMBOLS 1 Film-forming apparatus 2 Vacuum container 3 Cylindrical adhesion prevention member 4a, 4b Target 5 Back plate 6 Target holder 7 Substrate holder 8 Exhaust port 10 Substrate 12 Power supply 13 Target shutter 14 Target shutter drive mechanism 15 Reactive gas introduction mechanism 16a, 16b Reactive gas introduction part 17 Inert gas introduction mechanism 18 Inert gas introduction part 40 Shield 41 Pressure gauge 42 Gate valve 47 Main valve 48 Turbo molecular pump 49 Dry pump 63 Storage device 100 Main control part

Claims (7)

In a vacuum vessel in which two target holders to which targets of different materials are attached are arranged, in a state where an inert gas and a reactive gas are introduced into the vacuum vessel, a constant electric power is applied to each of the target holders. and applied, when forming a film containing a mixture of the two targets the substrate to the two by simultaneously sputtering target material, allowed to occur a reaction product with the two respective targets Due to the amount of the reactive gas being different for each target , during sputtering, one of the two targets is in a poison mode, the other of the two targets is in a metal mode, and the substrate has the 2 A film for a metal gate electrode containing a mixture of two target materials is deposited. Sputtering method comprising Rukoto. The sputtering method according to claim 1 , wherein the reactive gas is introduced only in the vicinity of the target in the poison mode. The sputtering method according to claim 1 , wherein the inert gas is introduced in the vicinity of a target to be the metal mode. Introducing an inert gas and reactive gas into the vacuum vessel, applying a certain amount of power to the aluminum target and the titanium target , respectively, and simultaneously sputtering the aluminum target and the titanium target to contain a mixture of aluminum and titanium on the substrate The amount of the reactive gas that reacts with the titanium target to generate a reaction product when forming the film to be reacted is greater than the amount of the reactive gas that reacts with the aluminum target to generate a reaction product. by large, the titanium target becomes poisoned mode, the aluminum target is a metal mode, the Rukoto film for metal gate electrode is deposited containing a mixture of the aluminum target and the titanium target material to a substrate Spattery features Grayed way. The sputtering method according to claim 4 , wherein the reactive gas is introduced only in the vicinity of the titanium target. The sputtering method according to claim 4 , wherein the inert gas is introduced in the vicinity of the aluminum target. Sputtering method according to any one of claims 4 to 6, wherein the reactive gas is nitrogen gas.