US20150167174A1

US20150167174A1 - Plating apparatus, plating method, and storage medium

Info

Publication number: US20150167174A1
Application number: US14/404,174
Authority: US
Inventors: Nobutaka Mizutani; Takashi Tanaka; Mitsuaki Iwashita
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2012-05-30
Filing date: 2013-05-27
Publication date: 2015-06-18
Also published as: KR20150016275A; KR102052131B1; TW201409573A; WO2013180063A1; JP2013249495A

Abstract

A plating method can improve uniformity in thickness of a plating layer formed on an inner surface of a recess. The plating method includes a loading process of loading the substrate in which the recess is formed into a casing; and a plating process of supplying a plating liquid to the substrate and forming a plating layer having a specific function on an inner surface of the recess. In the plating process, after supplying the plating liquid to the substrate and filling the plating liquid into the recess, a plating liquid having a higher temperature than a temperature of the plating liquid is supplied to the substrate.

Description

TECHNICAL FIELD

The embodiments described herein pertain generally to a plating method of performing a plating process to a recess formed in a substrate, a plating apparatus, and a storage medium.

BACKGROUND

In general, there is formed a circuit wiring on a substrate such as a semiconductor wafer or a liquid crystal substrate for forming a semiconductor device. As a method of forming a wiring, there has been used a damascene method in which a recess such as a via or a trench for burying a wiring material such as copper is formed in the substrate and the wiring material is buried in the recess.
Further, in recent years, there has been made an attempt to reduce a mounting area of a part or a whole system by mounting multiple LSIs on a substrate using a three-dimensional mounting technology. In the three-dimensional mounting technology, a recess, e.g., a through-silicon-via (TSV), for burying a wiring material, which connects the LSIs, is formed, for example, in a substrate (e.g., a silicon substrate).
Between an inner surface of a recess in a substrate and a wiring formed in the recess, typically, there is formed a barrier film for suppressing diffusion of atoms constituting a wiring material into an insulting film (an oxide film, PI “polyimide”, etc.) on the inner surface of the recess and into the substrate on a rear surface side thereof, or for improving adhesivity therebetween. Further, between the barrier film and the wiring, typically, there is formed a seed film for making it easy to bury the wiring material.
By way of example, in Patent Document 1, there is suggested a method in which a barrier film containing ruthenium is formed on an inner surface of a recess by sputtering, a seed film containing ruthenium and copper is formed on the barrier film by sputtering, and then, copper is buried in the recess by a plating process.

REFERENCES

Patent Document 1: Japanese Patent Laid-open Publication No. 2010-177538

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In recent years, there has been developed a manufacturing technique employing a TSV. In this manufacturing technique, a height or a depth of a recess in the TSV is not in a range of several tens of nanometers to several hundreds of nanometers in a conventional pre-treatment process but in a range of several microns to several hundreds of microns. For this reason, the conventional manufacturing technique may be employed in some cases, but a different method may be needed in some cases.
By way of example, a sputtering method which has been typically used for forming a barrier film or a seed film has a high directionality. For this reason, if a recess has a great height or depth, it is difficult to sufficiently form a barrier film or a seed film on a lower portion of the recess.
In order to solve such problems, a plating method such as an electroplating process or an electroless plating process may be considered. However, if a recess has a small diameter and a great height or depth, a plating liquid within the recess has a low fluidity, which may cause nonuniformity in concentration distribution of the plating liquid between an upper portion of the recess and a lower portion thereof. If there is nonuniformity in the concentration distribution of the plating liquid within the recess, it can be assumed that there is nonuniformity in distribution of density or a thickness of a plating layer such as a barrier film or a seed film formed on an inner surface of the recess.
In view of the foregoing problems, example embodiments provide a plating method capable of improving uniformity in thickness of a plating layer formed on an inner surface of a recess, a plating apparatus, and a storage medium.

Means for Solving the Problems

In accordance with a first aspect, a plating method of performing a plating process to a recess formed in a substrate includes a loading process of loading the substrate in which the recess is formed into a casing; and a plating process of supplying a plating liquid to the substrate and forming a plating layer having a specific function on an inner surface of the recess. In the plating process, after supplying the plating liquid to the substrate and filling the plating liquid into the recess, a plating liquid having a higher temperature than a temperature of the plating liquid is supplied to the substrate.
In accordance with a second aspect, a plating apparatus of performing a plating process to a recess formed in a substrate includes a substrate holding unit configured to hold the substrate in which the recess is formed; and a plating unit configured to supply a plating liquid to the substrate and form a plating layer having a specific function on an inner surface of the recess. After supplying the plating liquid to the substrate and filling the plating liquid into the recess, the plating unit is configured to supply a plating liquid having a higher temperature than a temperature of the plating liquid.
In accordance with a third aspect, a computer-readable storage medium has stored thereon computer-executable instructions that, in response to execution, cause a plating apparatus to perform a plating method of performing a plating process to a recess formed in a substrate. The plating method includes a loading process of loading the substrate in which the recess is formed into a casing; and a plating process of supplying a plating liquid to the substrate and forming a plating layer having a specific function on an inner surface of the recess and in the plating process, after supplying the plating liquid to the substrate and filling the plating liquid into the recess, a plating liquid having a higher temperature than a temperature of the plating liquid is supplied to the substrate.

Effect of the Invention

In accordance with the example embodiments, it is possible to improve uniformity in distribution of density or a thickness of a plating layer formed on an inner surface of a recess.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a plating apparatus in accordance with one example embodiment.

FIG. 2A and FIG. 2B are plane views of the plating apparatus illustrated in FIG. 1.

FIG. 3 is a diagram illustrating a film forming plating liquid supply unit configured to supply a high-temperature plating liquid to a film forming unit of a plating unit.

FIG. 4 is a diagram illustrating a substitution plating liquid supply unit configured to supply a low-temperature plating liquid to a substitution unit of the plating unit.

FIG. 5 is a flowchart showing a plating method.

FIG. 6A is a diagram illustrating a process of preparing a substrate in which a recess is formed.

FIG. 6B is a diagram illustrating a process of supplying a pre-treatment liquid into the recess.

FIG. 6C is a diagram illustrating a substitution process of substituting the pre-treatment liquid filled in the recess of the substrate with a low-temperature plating liquid.

FIG. 6D is a diagram illustrating a film forming process of supplying a high-temperature plating liquid to a substrate.

FIG. 6E is a diagram illustrating that a plating layer is formed on an inner surface of the recess.

FIG. 6F is a diagram illustrating a process of burying a wiring material in the recess.

FIG. 7 is a diagram illustrating that the pre-treatment liquid is substituted with the low-temperature plating liquid.

FIG. 8 is a diagram illustrating that multiple discharge nozzles of the film forming unit are supplying a plating liquid to the substrate.

FIG. 9 illustrates a modification example of the plating liquid supply unit.

FIG. 10 illustrates a modification example of the substitution unit.

FIG. 11 is a diagram illustrating a relationship between a diffusion time and a diffusion distance when components of the plating liquid are diffused in the substitution process.

FIG. 12 illustrates an example of a plating layer formed in an experimental example 1.

FIG. 13 illustrates an example of a plating layer formed in a comparative example 1.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, referring to FIG. 1 to FIG. 8, the example embodiments will be explained. Referring to FIG. 1, FIG. 2A and FIG. 2B, an overall configuration of a plating apparatus 20 will be explained first. FIG. 1 is a side view illustrating the plating apparatus 20, and FIG. 2A and FIG. 2B are plane views of the plating apparatus 20. Further, in the present example embodiment, there will be explained an example where the plating apparatus 20 is a single-substrate processing apparatus that performs a plating process to a single substrate 2 by discharging a plating liquid to the substrate 2.
Plating Apparatus
The plating apparatus 20 includes a substrate holding unit 110 configured to hold and rotate a substrate 2 within a casing 101; a plating unit 30 configured to discharge a plating liquid toward the substrate 2 held by the substrate holding unit 110 and form a plating layer having a specific function on an inner surface of a recess in the substrate; and a plating liquid supply unit connected to the plating unit 30 and configured to supply the plating liquid to the plating unit 30. The plating unit 30 includes a substitution unit 55 configured to discharge a low-temperature plating liquid toward the substrate 2; and a film forming unit 35 configured to discharge a high-temperature plating liquid, which has a temperature higher than that of the plating liquid discharged from the substitution unit 55, toward the substrate 2. Further, the term “low temperature” means that a plating reaction cannot proceed actively at the temperature of the plating liquid discharged from the substitution unit 55. By way of example, it means that a film forming rate of a plating layer formed of the plating liquid discharged from the substitution unit 55 has 10% or less of a film forming rate of a plating layer 15 finally formed of the high-temperature plating liquid. Further, the term “high temperature” means that a plating process can be completed within an allowable processing time at the temperature of the plating liquid discharged from the film forming unit 35.
Further, the plating liquid supply unit includes a film forming plating liquid supply unit 71 configured to supply the high-temperature plating liquid to the film forming unit 35 and a substitution plating liquid supply unit 74 configured to supply the low-temperature plating liquid to the substitution unit 55.
Furthermore, the plating apparatus 20 further includes a pre-treatment unit 54 configured to discharge a pre-treatment liquid toward the substrate 2. The pre-treatment unit 54 is connected to a pre-treatment liquid supply unit 73 configured to supply the pre-treatment liquid to the pre-treatment unit 54. The pre-treatment liquid is a liquid to be discharged toward the substrate 2 before the plating liquid is discharged toward the substrate 2. As the pre-treatment liquid, for example, deionized pure water, so-called deionized water (DIW), may be used.
Moreover, the plating apparatus 20 may further include a pre-wet unit 57 configured to discharge a pre-wet liquid toward the substrate 2. The pre-wet unit 57 is connected to a pre-wet liquid supply unit 76 configured to supply the pre-wet liquid to the pre-wet unit 57. The pre-wet liquid is a liquid to be supplied toward the substrate 2 in a dry state. With the pre-wet liquid, for example, affinity between a processing liquid to be subsequently supplied toward the substrate 2 and the substrate 2 can be increased. As the pre-wet liquid, ionized water containing ions of CO₂may be used.
Around the substrate holding unit 110, a liquid drain cup 120 including a first opening portion 121 and a second opening portion 126 and configured to receive a liquid such as the plating liquid or the pre-treatment liquid scattered from the substrate 2 and an exhaust cup 105 including an opening portion 106 for sucking a gas are arranged. Liquids received by the first opening portion 121 and the second opening portion 126 of the liquid drain cup 120 are drained out by a first liquid drain unit 122 and a second liquid drain unit 127, respectively. A gas sucked from the opening portion 106 of the exhaust cup 105 is exhausted by an exhaust unit 107. Further, the liquid drain cup 120 is connected to an elevation unit 164, and the elevation unit 164 can move the liquid drain cup 120 up and down. For this reason, the liquid drain cup 120 can be moved up and down according to a kind of a liquid scattered from the substrate 2, so that a path through which the liquid is drained out can be different for each kind of a liquid.
(Substrate Holding Unit)
As depicted in FIG. 2A and FIG. 2B, the substrate holding unit 110 includes a hollow cylindrical rotation shaft 111 vertically extended within the casing 101; a turn table 112 provided at an upper end of the rotation shaft 111; a wafer chuck 113 provided at an outer periphery of an upper surface of the turn table 112 and configured to support the substrate 2; and a rotation unit 162 connected to the rotation shaft 111 and configured to rotate and drive the rotation shaft 111.
The rotation unit 162 is controlled by a control unit 160 to rotate and drive the rotation shaft 111. Thus, the substrate 2 supported by the wafer chuck 113 is rotated. In this case, the control unit 160 controls the rotation unit 162, so that the rotation shaft 111 and the wafer chuck 113 can be rotated or the rotation thereof can be stopped. Further, the control unit 160 can increase or decrease the rotation number of the rotation shaft 111 and the wafer chuck 113, or can control the rotation number to be maintained at a certain value.
(Plating Unit)
Hereinafter, the film forming unit 35 and the substitution unit 55 of the plating unit 30 will be explained. The film forming unit 35 will be explained first. The film forming unit 35 includes a discharge nozzle 34 configured to discharge the plating liquid toward the substrate 2 and a discharge head 33 in which the discharge nozzle 34 is provided. Within the discharge head 33, a line through which the plating liquid supplied from the plating liquid supply unit 71 is introduced to the discharge nozzle 34 and a line through which a heat transfer medium for keeping heat of the plating liquid is circulated are accommodated.
The discharge head 33 is configured to be vertically and horizontally moved. By way of example, the discharge head 33 is provided at a front end of an arm 32, and the arm 32 is fixed at a supporting shaft 31 which can be vertically extended and can be rotated by a rotation unit 165. As depicted in FIG. 2A, with the rotation unit 165 and the supporting shaft 31, the discharge head 33 can be moved between a discharge position where the discharge head 33 discharges the plating liquid toward the substrate 2 and a stand-by position where the discharge head 33 does not discharge the plating liquid.
As depicted in FIG. 1, the discharge head 33 may be extended to have a length corresponding to a length from a central portion of the substrate 2 to a peripheral portion of the substrate 2, i.e., the radius of the substrate 2. In this case, in the discharge head 33, there may be provided multiple discharge nozzles 34 configured to discharge the plating liquid. In this case, when the plating liquid is discharged, the discharge head 33 is positioned such that the multiple discharge nozzles 34 are arranged along a radial direction of the substrate 2, and, thus, it is possible to supply the plating liquid throughout a wide area of the substrate 2 at the same time. Further, although not illustrated, the discharge nozzles 34 provided in the discharge head 33 may be extended along the radial direction of the substrate 2 and configured to discharge the plating liquid toward the substrate 2. Even in this case, it is possible to supply the plating liquid throughout a wide area of the substrate 2 at the same time.
Hereinafter, the substitution unit 55 will be explained. As depicted in FIG. 1, the first substitution unit 55 includes a discharge nozzle 55 a configured to discharge the plating liquid toward the substrate 2; and a discharge head 53 in which the discharge nozzle 55 a is provided. The discharge head 53 is configured to be vertically and horizontally moved. By way of example, the discharge head 53 of the substitution unit 55 is provided at a front end of an arm 52 in the same manner as the discharge head 33 of the film forming unit 35. The arm 52 is fixed at a supporting shaft 51 which can be vertically extended and can be rotated by a rotation unit 166. In this case, as depicted in FIG. 2B, the discharge head 53 can be horizontally rotated about an axis of the supporting shaft 51 between a position corresponding to the central portion of the substrate 2 and a position corresponding to the peripheral portion of the substrate 2.
(Plating Liquid Supply Unit)
Hereinafter, referring to FIG. 3, there will be explained the film forming plating liquid supply unit 71 and the substitution plating liquid supply unit 74 of the plating liquid supply unit respectively configured to supply the plating liquid to the film forming unit 35 and the substitution unit 55 of the plating unit 30. Further, the film forming plating liquid supply unit 71 and the substitution plating liquid supply unit 74 are different from each other only in whether or not a heating unit configured to heat the plating liquid is provided and have the same configuration except such a difference. Herein, the film forming plating liquid supply unit 71 will be mainly explained.
As depicted in FIG. 3, the plating liquid supply unit 71 includes a tank 71 b configured to store and preserve therein a plating liquid 71 c; and a supply line 71 a through which the plating liquid 71 c stored within the tank 71 b is supplied to the plating unit 30. The supply line 71 a includes a pump 71 e and a valve 71 d for controlling a flow rate of the plating liquid 71 c. Further, at the tank 71 b, there is provided a heating unit 71 g configured to heat the plating liquid 71 c stored in the tank 71 b.
(Plating Liquid)
Hereinafter, the plating liquid used in the present example embodiment will be explained. Further, a plating liquid to be supplied from the film forming plating liquid supply unit 71 to the film forming unit 35 and a plating liquid to be supplied from the substitution plating liquid supply unit 74 to the substitution unit 5 are substantially the same except a temperature thereof. Hereinafter, the term “plating liquid” to be used when explaining a material or a component of the plating liquid refers to both of the plating liquid to be used in the film forming unit 35 and the plating liquid to be used in the substitution unit 55.
The plating liquid contains a material corresponding to the plating layer formed on the surface of the substrate 2 and having a specific function. By way of example, if the plating layer formed on the substrate 2 by the plating apparatus 20 serves as a barrier film that suppresses permeation of a metal material constituting a wiring into an insulating film or the substrate 2, the plating liquid contains Co (cobalt), W (tungsten), or Ta (tantalum) to be used as a material of the barrier film. Further, if the plating layer formed on the substrate 2 by the plating apparatus 20 serves as a seed film configured to allow a wiring material, the plating liquid contains Cu (copper) to be used as a wiring material to be easily buried. In addition, the plating liquid may contain a complexing agent, or a reducing agent (a compound containing B (boron) and P (phosphor)), and a surfactant depending on a material contained therein or a kind of a plating reaction.
Further, the plating liquid may contain an additive which can affect a plating reaction rate. The additive can be appropriately selected depending on materials contained in the plating liquid. By way of example, if the plating liquid contains Co and W to be used as a material of the barrier film, the plating liquid contains bis (3-sulfopropyl) disulfide, so-called SPS, as the additive.
(Pre-Treatment Unit and Pre-Wet Unit)
Hereinafter, the pre-treatment unit 54 and the pre-wet unit 57 will be explained. The pre-treatment unit 54 includes a discharge nozzle 54 a configured to discharge a pre-treatment liquid toward the substrate 2. In the same manner, the pre-wet unit includes a discharge nozzle 57 a configured to discharge a pre-wet liquid toward the substrate 2. As depicted in FIG. 1, each of the discharge nozzles 54 a and 57 a may be provided in the above-described discharge head 53 that can be vertically and horizontally moved.
(Pre-Treatment Liquid Supply Unit and Pre-Wet Liquid Supply Unit)
Hereinafter, referring to FIG. 4, there will be explained the pre-treatment liquid supply unit 73 configured to supply the pre-treatment liquid to the pre-treatment unit 54 and a pre-wet liquid supply unit 76 configured to supply the pre-wet liquid toward the pre-wet unit 57. Further, the pre-treatment liquid supply unit 73 and the pre-wet liquid supply unit 76 are different from each other only in a kind of a processing liquid and have the same configuration except such a difference. Herein, the pre-treatment liquid supply unit 73 will be mainly explained.
As depicted in FIG. 4, the pre-treatment liquid supply unit 73 includes a tank 73 b configured to store a pre-treatment liquid 73 c such as DIW; and a supply line 73 a configured to supply the pre-treatment liquid 73 c stored within the tank 73 b to the pre-treatment unit 54. The supply line 73 a includes a pump 73 e and a valve 73 d for regulating a flow rate of the pre-treatment liquid 73 c.
Further, the pre-treatment liquid supply unit 73 may further include a deaeration device 73 f configured to remove a gas such as dissolved oxygen or dissolved hydrogen in the pre-treatment liquid 73 c. As depicted in FIG. 4, the deaeration device 73 f may be configured as a gas supply line for supplying an inert gas such as nitrogen to the pre-treatment liquid 73 c stored in the tank 73 b. Thus, the inert gas can be dissolved in the pre-treatment liquid 73 c, so that oxygen or hydrogen already dissolved in the pre-treatment liquid 73 c can be discharged to the outside. That is, a deaeration process can be performed on the pre-treatment liquid 73 c. A degree of the deaeration process performed by the deaeration device 73 f is not particularly limited. However, for example, the deaeration process may be performed such that an oxygen concentration in the cleaning liquid 73 c to be discharged toward the substrate 2 is 1 ppm or less, and desirably, 0.5 ppm or less.
The plating apparatus 20 configured as described above is controlled by a control unit 160 according to various programs recorded in a storage medium 161 provided in the control unit 160. Thus, various processes are performed to the substrate 2. Herein, the storage medium 161 stores various setting data or various programs such as a plating process program to be described later. As the storage medium 161, a publicly known storage medium such as a computer-readable memory, e.g., a ROM or a RAM, or a hard disc, a disc-shaped storage medium, e.g., a CD-ROM, a DVD-ROM, or a flexible disc may be used.
Plating Method
Hereinafter, an operation and an effect of the present example embodiment configured as described above will be explained. There will be explained a plating method of forming a barrier film of CoWB by an electroless plating process on an inner surface of the recess 12 formed in the substrate 2. FIG. 5 is a flowchart showing the plating method. Further, FIG. 6A to FIG. 6F are cross-sectional views illustrating the substrate 2 in the respective processes of the plating method.
Firstly, the recess 12 for burying a wiring material is formed in the substrate 2. As a method of forming the recess 12 in the substrate 2, one of the conventionally known methods may be appropriately employed. To be specific, for example, as a dry etching technique, a general-purpose technique using a fluorine-based or chlorine-based gas may be employed. In particular, in order to form the recess 12 having a high aspect ratio (ratio of a depth of a hole to a diameter thereof), a method using an ICP-RIE (Inductively Coupled Plasma Reactive Ion Etching) technique capable of deep-etching at a high speed may be employed more appropriately. In particular, a so-called Bosch process in which an etching process using a sulphur hexafluoride (SF₆) and a protection process using a Teflon-based gas such as C₄F₈are repeatedly performed may be appropriately employed.
A shape of the recess 12 is not particularly limited as long as a movement of each component of the plating liquid within the recess 12 is based on mainly the diffusion instead of on the flow. By way of example, an aspect ratio of the recess 12 is in a range of 5 to 30. To be specific, if a horizontal cross section of the recess has a circular shape, a diameter of the recess 12 is in a range of 0.5 μm to 20 μm, for example, 8 μm. Further, a height or depth of the recess 12 is in a range of 10 μm to 250 μm, for example, 100 μm. Then, an insulating film is formed within the recess 12. As a method of forming the insulating film, for example, a method of forming a silicon oxide film (SiO₂) by a CVD (Chemical Vapor Deposition) method is used.
Then, the substrate 2 is prepared within the casing 101. In the pre-wet unit 57, a pre-wet liquid 76 c is discharged toward the substrate 2 (Pre-wet process (S10)). Thus, as depicted in FIG. 6A, the surface of the substrate 2, for example, the inner surface 12 a of the recess 12 and the upper surface of the substrate 2, may be brought into contact with the pre-wet liquid 76 c. Thus, the affinity between the surface of the substrate 2 and the pre-treatment liquid to be supplied to the substrate 2 can be increased. As the pre-wet liquid 76 c, for example, ionized water containing ions of CO₂may be used.
Then, in the pre-treatment unit 54, the pre-treatment liquid 73 c is discharged toward the substrate 2 (Pre-treatment process (S20)). Thus, as depicted in FIG. 6B, the inside of the recess 12 is filled with the pre-treatment liquid 73 c. As the pre-treatment liquid 73 c, for example, DIW on which a deaeration process is performed may be used.
Thereafter, in the plating unit 30, the plating liquid 71 c for forming a film of CoWB is discharged toward the substrate 2 (Plating process (S21)). The plating process (S21), as depicted in FIG. 5, includes a substitution process (S21 a) of discharging a low-temperature plating liquid 74 c toward the substrate 2 and a film forming process (S21 b) of discharging a high-temperature plating liquid 71 c toward the substrate 2.
In the substitution process (S21 a), substitution plating liquid supply unit 74 supplies the low-temperature plating liquid 74 c to the substitution unit 55. The supplied plating liquid 74 c has a temperature, for example, a room temperature (25° C.), at which a plating reaction cannot proceed actively. Then, the plating liquid 74 c is discharged toward the substrate 2 from the discharge nozzle 55 a provided in the discharge head 53.
As described above, the recess 12 formed in the substrate 2 has a high aspect ratio. Further, a depth of the recess 12 is remarkably increased as compared with a depth of the conventional recess, and it is, for example, 100 μm. If the plating liquid 74 c is supplied into the deep recess 12, each component contained in the plating liquid 74 c reaches to the bottom of the recess 12 based on mainly the diffusion in the plating liquid. Meanwhile, diffusion is a phenomenon that gradually proceeds as times passes. For this reason, each component of the plating liquid 74 c takes a preset time to sufficiently reach to the bottom of the recess 12. Therefore, the substitution process (S21 a) of supplying the plating liquid 74 c toward the substrate 2 is continuously performed for a preset time to sufficiently substitute the pre-treatment liquid 73 c within the recess 12 with the plating liquid 74 c.
Hereinafter, there will be explained an example of a method for determining a continuation time of the substitution process (S21 a).
Generally, abnormal diffusion in a plating liquid can be represented by the Fick's second law of diffusion as follows:
$\begin{matrix} \frac{\partial C}{\partial t} = D \frac{\partial^{2} C}{\partial x^{2}} & [Equation 1] \end{matrix}$
Herein, D is a diffusion coefficient of a component to be diffused; C is a concentration of the component to be diffused; t is a time; and x is a distance from a reference position. A relationship between a diffusion time and a diffusion distance when a plating component (a component of a material constituting a plating layer) in a plating liquid is calculated based on the Fick's second law of diffusion and a result thereof is as shown in FIG. 11. In FIG. 11, the horizontal axis represents a time, and the longitudinal axis represents a distance from an upper end of the recess 12. Further, the calculation is carried out on the presumption that in the case of time (t)=0, the inside of the recess 12 is filled with the pre-treatment liquid 73 c only, and in the case of time (t)=0, the liquid present above the upper end of the recess 12 is substituted with the plating liquid 74 c. Furthermore, a depth of the recess 12 is presumed infinite. Further, in FIG. 11, the solid line or the dashed lines annotated as “x % (x=50, 65, 80, 88, or 95)” represent a diffusion time required for a concentration of a plating component at a corresponding distance to reach x % of a concentration of a plating component at the upper end of the recess 12. By way of example, in FIG. 11, the dot with symbol A means a diffusion time of 600 seconds which is required for a concentration of a plating component at a position 70 μm away from the upper end of the recess 12 to reach 95% of a concentration of a plating component at the upper end of the recess 12.
Based on the relationship as shown in FIG. 11, a continuation time of the substitution process (S21 a) can be determined. By way of example, as for the recess 12 having a depth of 100 μm, if a concentration of a plating component at the bottom of the recess 12 is required to reach about 90% of a concentration of a plating component of the plating liquid 74 c supplied to the substrate 2, a continuation time of the substitution process (S21 a) is set to about 600 seconds. Since the substitution process (S21 a) is continued for such a long time, the plating liquid 74 c can sufficiently reach to the bottom of the recess 12. Thus, a concentration distribution of the plating liquid 74 c filled in the recess 12 can be substantially uniform.
Further, in the present example embodiment, as described above, the temperature of the plating liquid 74 c to be supplied to the substrate 2 in the substitution process (S21 a) is set to a low level at which a plating reaction cannot proceed actively. By way of example, the temperature of the plating liquid 74 c is set such that a film forming rate of a plating layer formed during the substitution process (S21 a) has 10% or less of a film forming rate of the plating layer 15 finally formed of the high-temperature plating liquid. For this reason, it is possible to suppress significant progress of a plating reaction before the plating liquid 74 sufficiently reaches to the bottom of the recess 12.
Then, the film forming unit 35 discharges a high-temperature plating liquid 71 c toward the substrate 2 (Film forming process (S21 b)). To be specific, the film forming plating liquid supply unit 71 supplies the plating liquid 71 c heated to a high temperature to the film forming unit 35. The supplied plating liquid 71 c has a temperature, for example, 45° C., at which a plating reaction can proceed at an appropriate rate. Then, as depicted in FIG. 8, the plating liquid 71 c is discharged toward the substrate 2 from the multiple discharge nozzles 34 arranged in parallel with each other along the radial direction of the substrate 2. Thus, it is possible to supply the plating liquid 71 c throughout a wide area of the substrate 2 at the same time. Thus, a temperature distribution of the plating liquid 71 c on the substrate 2 can be substantially uniform regardless of positions on the substrate 2. By way of example, a temperature of the plating liquid 71 c reaching a central portion of the substrate 2 can be substantially equal to a temperature of the plating liquid 71 c reaching a peripheral portion of the substrate 2.
When the film forming process (S21 b) is started, as described above, the low-temperature plating liquid 74 c has been already filled in the recess 12l In this case, if the high-temperature plating liquid 71 c is supplied to the substrate 2, above the upper end of the recess 12, i.e., above an upper surface 11 a of an insulating layer 11, the low-temperature plating liquid 74 c is substituted with the high-temperature plating liquid 71 c. Then, the low-temperature plating liquid 74 c filled in the recess 12 is heated by heat from the high-temperature plating liquid 71 c. Herein, generally, a velocity of thermal conduction in a liquid is higher than a velocity of diffusion of the component in the liquid. For this reason, the low-temperature plating liquid 74 c within the recess 12 is rapidly heated to be changed into the high-temperature plating liquid 71 c. That is, the inside of the recess 12 can be rapidly filled with the high-temperature plating liquid 71 c. Further, although the plating liquid 74 c and the plating liquid 71 c are assigned different reference numerals, they are substantially the same except the temperature thereof as described above. Therefore, by heating the low-temperature plating liquid 74 c, it is possible to substitute or change the low-temperature plating liquid 74 c into the high-temperature plating liquid 71 c.
When the inside of the recess 12 is filled with the high-temperature plating liquid 71 c, as depicted in FIG. 6E, the plating layer 15 is formed on the inner surface 12 a of the recess 12. Herein, as described above, the high-temperature plating liquid 71 c within the recess 12 is obtained by heating the low-temperature plating liquid 74 c having a substantially uniform concentration distribution within the recess 12. For this reason, in accordance with the present example embodiment, a concentration distribution of the plating liquid 71 c within the recess 12 can be uniform as compared with the case where the substitution process is not performed in advance. Thus, the plating reaction in the film forming process (S21 b) can be started with the plating liquid 71 c having a substantially uniform concentration distribution regardless of the positions within the recess 12. Accordingly, uniformity in thickness or density distribution of the plating layer 15 formed on the inner surface 12 a of the recess 12 can be increased.
Then, post-treatments including rinsing processes (S32 and S40) of discharging a rinse liquid toward the substrate 2, a post-cleaning process (S33) of discharging a post-cleaning liquid toward the substrate 2, and a drying process (S41) of drying the substrate 2 with air or IPA are carried out. As such, the substrate 2 on which the barrier film of the plating layer 15 is formed can be obtained.
Then, as depicted in FIG. 6F, a seed film 16 may be formed on the barrier film of the plating layer 15. Further, a wiring 17 including a metal material such as copper may be formed within the recess 12 covered with the seed film 16. A method of forming the seed film 16 and the wiring 17 is not particularly limited, but, for example, an electroless plating method may be used. Herein, in the same manner as the case of forming the barrier film of the plating layer 15, a two plating processes using two kinds of plating liquids different in the temperature may be performed.
In accordance with the present example embodiment, as described above, the plating process (S21) includes the substitution process (S21 a) using the low-temperature plating liquid 74 c and the film forming process (S21 b) using the high-temperature plating liquid 71 c. Since the plating process divided into the two processes is performed as such, when a plating reaction is carried out with the high-temperature plating liquid 71 c, a concentration distribution of the high-temperature plating liquid 71 c within the recess 12 can be substantially uniform regardless of the positions within the recess 12. Thus, uniformity in thickness or density distribution of the plating layer 15 formed on the recess 12 can be increased.
Further, in accordance with the present example embodiment, as described above, the DIW on which a deaeration process is performed is used as the pre-treatment liquid 73 c to be supplied to the substrate 2 in the pre-treatment process (S20). For this reason, it is possible to suppress bubbles caused by the dissolved gas in the pre-treatment liquid 73 c from being formed on the surface of the substrate 2 including the inner surface 12 a of the recess 12. Thus, a plating reaction can efficiently proceed on the surface of the substrate 2 without being affected by the bubbles, so that the plating layer 15 can be formed on the surface of the substrate 2 uniformly.
Furthermore, in accordance with the present example embodiment, as described above, the ionized water containing ions of CO₂is used as the pre-wet liquid to be supplied to the substrate 2 in the pre-wet process (S10). For this reason, as compared with the case where an electrically neutral processing liquid such as DIW is supplied to the substrate 2 in advance, it is possible to suppress electric discharge from occurring during the plating process.
Moreover, in accordance with the present example embodiment, as described above, the plating liquid 71 c is discharged toward the substrate 2 from the multiple discharge nozzles 34 arranged in parallel with each other along the radial direction of the substrate 2. For this reason, a temperature distribution of the plating liquid 71 c on the substrate 2 can be substantially uniform regardless of the positions on the substrate 2. Thus, a thickness of the plating layer 15 formed on the substrate 2 can also be uniform regardless of the positions on the substrate 2.

MODIFICATION EXAMPLE

Further, in the substitution process (S21 a) of the present example embodiment, as depicted in FIG. 7, while the discharge head 53 is moved along a direction indicated by the arrow S, the low-temperature plating liquid 74 c may be discharged toward the substrate 2 from the discharge nozzle 55 a provided in the discharge head 53. In this case, a velocity component corresponding to a moving speed of the discharge head 53 is added to a velocity component of the discharged plating liquid 74 c. For this reason, it is possible to increase a pressing force of the plating liquid 74 c against the pre-treatment liquid 73 c along the direction S. Further, an impact force based on kinetic energy of the plating liquid 74 c can be directly applied to the pre-treatment liquid 73 c filled in each recess 12. Thus, efficiency of substitution of the pre-treatment liquid 73 c with the plating liquid 74 c can be increased.
Further, the direction indicted by the arrow S is parallel with, for example, a direction from the central portion of the substrate 2 toward the peripheral portion of the substrate 2.
Furthermore, in the present example embodiment, the heating unit 71 g configured to heat the plating liquid 71 c to be supplied to the plating unit 30 is provided at the tank 71 b. However, an aspect for heating the plating liquid 71 c is not limited thereto. By way of example, the heating unit 71 g may be provided at the supply line 71 a instead of at the tank 71 b.
Moreover, in the present example embodiment, the tank 71 b configured to supply the high-temperature plating liquid 71 c into the film forming unit 35 and the tank 74 b configured to supply the low-temperature plating liquid 74 c into the substitution unit 55 are separately provided. However, the present example embodiment is not limited thereto. A tank configured to supply the high-temperature plating liquid 71 c into the film forming unit 35 and a tank configured to supply the low-temperature plating liquid 74 c into the substitution unit 55 may be commonly provided. By way of example, as depicted in FIG. 9, the tank 74 b in which the low-temperature plating liquid 74 c is stored may be used as a single common tank. In this case, as depicted in FIG. 9, the heating unit 71 g configured to heat a plating liquid is provided at the supply line 71 a of the film forming plating liquid supply unit 71. Thus, with the single common tank, it is possible to supply the high-temperature plating liquid 71 c into the film forming unit 35 and also possible to supply the low-temperature plating liquid 74 c into the substitution unit 55.
Further, in some cases, a plating liquid heated by the heating unit 71 g may be required not to be supplied to the substrate 2, but to be returned back to the tank 74 b. In this case, although not illustrated, a collecting line for returning the high-temperature plating liquid back to the tank 74 b may be further provided. Furthermore, a cooling unit for cooling a plating liquid may be provided at the collecting line. Thus, a plating liquid cooled to a low temperature can be returned to the tank 74 b. Moreover, the cooling unit provided at the collecting line and the above-described heating unit 71 g provided at the supply line 71 a may be configured as an integrated heat exchanger.
Furthermore, in the present example embodiment, the discharge nozzle 34 configured to discharge the high-temperature plating liquid 71 c and the discharge nozzle 55 a configured to discharge the low-temperature plating liquid 74 c are separately provided. However, the present example embodiment is not limited thereto. A discharge nozzle configured to discharge the high-temperature plating liquid 71 c and a discharge nozzle configured to discharge the low-temperature plating liquid 74 c may be commonly provided.
Moreover, in the film forming process (S21 b) of the present example embodiment, the low-temperature plating liquid 74 c already filled in the recess 12 is heated by supplying the high-temperature plating liquid 71 c toward the substrate 2. However, a method of using a high-temperature plating liquid with respect to the substrate 2 is not limited thereto. By way of example, by heating the substrate 2 or the turn table 112, the low-temperature plating liquid 74 c already filled in the recess 12 in the substrate 2 can be heated, so that the high-temperature plating liquid 71 c can be obtained. Herein, a method of heating the substrate 2 is not particularly limited, and various methods may be used. By way of example, as depicted in FIG. 10, the film forming unit 35may further include a substrate heating unit 36 configured to heat the substrate 2. As the substrate heating unit, there may be used a lamp heater 36 configured to irradiate light toward the substrate 2 to heat the substrate 2. Further, the substrate heating unit 36 may be configured to circulate a heat transfer medium such as hot water below the substrate 2 to heat the substrate 2. If the substrate 2 is heated from the below, a plating liquid filled in the recess 12 is heated from a lower side of the recess 12. It is advantageous to heat a plating liquid from the lower side of the recess 12 in the case of using a plating liquid for forming the plating layer first on the upper portion of the recess 12. This is because a plating reaction can be first started at the lower portion of the recess 12 by heating the plating liquid from the lower side of the recess 12. As a result, it is possible to reduce a difference between a thickness of the plating layer formed on the lower portion of the recess 12 and a thickness of the plating layer formed on the upper portion of the recess 12.
Further, in the present example embodiment, the barrier film formed of the plating layer 15 is directly formed on the inner surface 12 a of the recess 12 formed in the insulating layer 11. However, the present example embodiment is not limited thereto. Another layer may be interposed between the inner surface 12 a of the recess 12 and the barrier film. By way of example, a catalyzer layer for promoting a plating reaction may be interposed between the inner surface 12 a of the recess 12 and the barrier film. A material of the catalyzer layer is appropriately selected depending on the material of the plating layer. By way of example, if the plating layer is formed of CoWB, the material of the catalyzer layer may be Pd (palladium). An adhesion layer for improving adhesivity between the inner surface 12 a of the recess 12 and the catalyzer layer may be further formed. The adhesion layer may be formed by performing a SAM process using a coupling agent such as a silane coupling agent. Further, an insulating film such as TEOS or PI (polyimide) may be formed on the inner surface 12 a of the recess 12.
Furthermore, in the present example embodiment, the plating apparatus 20 is a single-substrate processing apparatus that performs a plating process to a single substrate 2 by discharging a plating liquid to the substrate 2. However, a plating apparatus to which the technical concept of the present example embodiment can be applied is not limited to the single-substrate processing apparatus. By way of example, the plating apparatus in accordance with the present example embodiment may be a so-called dip-type processing apparatus capable of performing plating process to multiple substrates 2 in a lump. In the dip-type processing apparatus, by dipping the substrate 2 into a plating tank in which a plating liquid is stored, the plating liquid is supplied to the substrate 2. The other configuration thereof is substantially the same as the above-described single-substrate plating apparatus 20, and detailed explanation thereof will be omitted.
Although several modification examples of the above-described example embodiments have been explained, it is possible to apply an appropriate combination of the multiple modification examples.

EXPERIMENTAL EXAMPLE

Experimental Example 1

There will be explained an example where the plating layer 15 of CoWB is formed on the inner surface 12 a of the recess 12 formed in the insulating layer 11 of the substrate 2 by using the above-described plating apparatus 20.
Firstly, the substrate 2 including the insulating layer 11 in which the recess 12 is formed is prepared. A diameter of the recess 12 is 8 μm, and a depth of the recess 12 is 100 μm.
Then, the pre-wet process (S 10) is performed. Thereafter, the pre-treatment process (S20) of discharging the pre-treatment liquid toward the substrate 2 is performed. Thus, the inside of the recess 12 is filled with the pre-treatment liquid. As the pre-treatment liquid, DIW on which the deaeration process is performed is used.
Then, the plating process (S21) of forming the plating layer 15 on the inner surface 12 a of the recess 12 is performed. To be specific, the substitution process (S21 a) of discharging the plating liquid having a temperature of 25° C. toward the substrate 2 is performed for 20 minutes. Then, the film forming process (S21 b) of discharging a plating liquid having a temperature of 65° C. toward the substrate 2 is performed for 5 minutes. A concentration of SPS contained in each plating liquid is 5 ppm. Thereafter, an appropriate post-treatment such as the rinsing process (S32) is performed.
The plating layer formed by the plating process (S21) is observed. To be specific, the plating layer formed at the upper portion of the recess 12 and the lower portion (bottom) thereof is observed. A result thereof is as shown in FIG. 12.

Comparative Example 1

A plating layer of CoWB is formed on the inner surface 12 a of the recess 12 in the substrate 2 in the same manner as the experimental example 1 except that the above-described substitution process (S21 a) is not performed. That is, in the comparative example 1, as a plating process, only the process of discharging the plating liquid having a temperature of 65° C. toward the substrate 2 is performed for 5 minutes. The formed plating layer is observed. A result thereof is as shown in FIG. 13.
As depicted in FIG. 13, in the comparative example 1, there are many portions where the plating layer is not formed on the inner surface 12 a of the recess 12. Meanwhile, as depicted in FIG. 12, in the experimental example 1, the plating layer can be uniformly formed on the inner surface 12 a of the recess b 12 including both of the upper portion of the recess 12 and the lower portion thereof. In the experimental example 1, each component of the plating liquid can be sufficiently diffused within the recess 12 by performing the substitution process prior to the film forming process, so that the plating layer can be uniformly formed on the inner surface 12 a of the recess 12.

EXPLANATION OF REFERENCE NUMERALS

2: Substrate
12: Recess
15: Plating layer
20: Plating apparatus
30: Plating unit
101: Casing
110: Substrate holding unit

Claims

1. A plating method of performing a plating process to a recess formed in a substrate, the plating method comprising:

a loading process of loading the substrate in which the recess is formed into a casing; and

a plating process of supplying a plating liquid to the substrate and forming a plating layer having a specific function on an inner surface of the recess,

wherein, in the plating process, after supplying the plating liquid to the substrate and filling the plating liquid into the recess, a plating liquid having a higher temperature than a temperature of the plating liquid is supplied to the substrate.

2. The plating method of claim 1, further comprising:

a pre-treatment process of supplying a pre-treatment liquid to the substrate,

wherein the plating process includes a substation process of supplying the plating liquid to the substrate and substituting the pre-treatment liquid filled into the recess in the substrate with the plating liquid, and a film forming process of forming the plating layer by supplying the plating liquid to the substrate after the substitution process, and

a temperature of the plating liquid used in the substitution process is set to be lower than a temperature of the plating liquid used in the film forming process.

3. The plating method of claim 2,

wherein the film forming process includes a process of supplying a plating liquid heated to a temperature higher than the temperature of the plating liquid used in the substitution process to the substrate.

4. The plating method of claim 2,

wherein the film forming process includes a process of heating the plating liquid supplied to the substrate to a temperature higher than the temperature of the plating liquid used in the substitution process.

5. The plating method of claim 2,

wherein the pre-treatment liquid is formed of deionized water on which a deaeration process is performed.

6. The plating method of claim 5, further comprising:

a pre-wet process of supplying ionized water containing ions to the substrate before the pre-treatment process.

7. The plating method of claim 2,

wherein, in the film forming process, the plating liquid is discharged from multiple discharge nozzles arranged in parallel with each other along a radial direction of the substrate or discharged from a discharge nozzle extended along the radial direction of the substrate.

8. A plating apparatus of performing a plating process to

a recess formed in a substrate, the plating apparatus comprising:

a substrate holding unit configured to hold the substrate in which the recess is formed; and

a plating unit configured to supply a plating liquid to the substrate and form a plating layer having a specific function on an inner surface of the recess,

wherein, after supplying the plating liquid to the substrate and filling the plating liquid into the recess, the plating unit is configured to supply a plating liquid having a higher temperature than a temperature of the plating liquid.

9. The plating apparatus of claim 8, further comprising:

a pre-treatment unit configured to supply a pre-treatment liquid to the substrate,

wherein the plating unit includes a substitution unit configured to supply the plating liquid for substituting the pre-treatment liquid filled into the recess in the substrate to the substrate, and a film forming unit configured to supply the plating liquid to the substrate after the substitution unit supplies the plating liquid to the substrate, and

a temperature of the plating liquid used in the substitution unit is set to be lower than a temperature of the plating liquid used in the film forming unit.

10. The plating apparatus of claim 9,

wherein the film forming unit is configured to supply a plating liquid heated to a temperature higher than the temperature of the plating liquid used in the substitution unit to the substrate.

11. The plating apparatus of claim 9,

wherein the film forming unit is configured to heat the plating liquid supplied to the substrate to a temperature higher than the temperature of the plating liquid used in the substitution unit.

12. The plating apparatus of claim 9,

13. The plating apparatus of claim 12, further comprising:

a pre-wet unit configured to supply ionized water containing ions to the substrate before supplying the pre-treatment liquid to the substrate.

14. The plating apparatus of claim 9,

wherein the film forming unit includes multiple discharge nozzles arranged in parallel with each other along a radial direction of the substrate and configured to discharge the plating liquid to the substrate, or a discharge nozzle extended along the radial direction of the substrate and configured to discharge the plating liquid to the substrate.

15. A computer-readable storage medium having stored thereon computer-executable instructions that, in response to execution, cause a plating apparatus to perform a plating method of performing a plating process to a recess formed in a substrate,

wherein the plating method comprises: