JP2003332260A - Method and device for forming silicide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and speedily form metallic silicide with less impurity on a surface of a wafer such as a semiconductor wafer with fewer processes and less foot printing. <P>SOLUTION: Silicon on the surface of the wafer is brought into contact with molten metal 42. Metal 42 and silicon are made into alloy and metallic silicide is formed. A silicide forming device is provided with a wafer holder 40 which freely attachably and detachably holds the wafer W having silicon on the surface, a melting basin 44 melting and holding metal forming metallic silicide by making metal and silicon on the surface of the wafer into alloy and a moving mechanism which relatively moves the wafer holder 40 and the melting basin 44 and brings the surface of the wafer W held by the wafer holder 40 into contact with molten metal 42 held by the melting basin. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicide forming method and apparatus for forming a metal silicide, which is an alloy with silicon, on the surface of a substrate such as a semiconductor wafer.

[0002]

2. Description of the Related Art When silicon is reacted with a refractory metal, a transition metal, a noble metal, etc. at a high temperature, the resistivity is low and the heat resistance,
A metal silicide having oxidation resistance is formed. This metal silicide is widely used in a semiconductor device as a gate electrode of a MOS transistor, a wiring material that can withstand a high temperature process, and the like.

As a method of forming silicide, for example, nickel silicide, on the surface of a substrate such as a semiconductor wafer, as shown in FIG. 6A, silicon 10 is deposited on the surface of a substrate W by sputtering or CVD. Then, as shown in FIG. 6B, nickel (metal) 12 is deposited on the surface of the silicon 10 by a plating method or a sputtering method, and then the substrate W is heat-treated at about 400 ° C., for example. Silicon 10 and nickel 12 react with each other to form an alloy, which causes nickel silicide (Ni _x
A solid-phase reaction method for forming Si _y ) 14, a silicide sputtering method using a target obtained by mixing and pressing metal and silicon, and the like are generally known. In the case of a substrate having silicon exposed on the surface, nickel (metal) silicide is formed on the surface of the substrate by depositing a metal such as nickel on the surface and performing heat treatment.

FIG. 7 shows a substrate processing in which a nickel silicide is formed on the surface of a substrate having silicon deposited on the surface or a substrate having silicon exposed on the surface by a solid-phase reaction method using electroless plating. The whole layout drawing of an apparatus is shown.
This device comprises a loading / unloading unit 20 for mounting a cassette containing a substrate and HCl on the surface of silicon.
And the like, a pretreatment unit 22 for performing pretreatment, a catalyst imparting unit 24 for imparting a catalyst such as Pd to the surface of the pretreated silicon, an electroless plating unit 26, a heat treatment unit 28, and between these units. It has a transfer robot 30 for transferring the substrate.

In this apparatus, the transfer robot 30 takes out the substrates one by one from the load / unload unit 20 and transfers them to the pretreatment unit 22 to bring a chemical solution such as HCl into contact (immersion) with the silicon surface. Pretreatment. Then, after washing with water, the pretreated substrate is conveyed to the catalyst applying unit 24, and becomes a catalyst for electroless plating.
In order to deposit d and the like on the surface of silicon, substitution treatment with a PdCl ₂ solution or the like is performed. After that, it is washed with water, and the substrate after the substitution process is conveyed to the electroless plating unit 26,
The surface of silicon is nickel-plated by immersing it in an electroless nickel plating solution. Then, the plated substrate is conveyed to the heat treatment unit 28 and heated to, for example, about 400 ° C. to form nickel silicide in which silicon and nickel are alloyed on the surface of the substrate, and the substrate on which the nickel silicide is formed is formed. The transfer robot 30 returns the cassette to the loading / unloading unit 20.

[0006]

However, in the above-mentioned conventional example, many steps are required to form the metal silicide, such as pretreatment for Pd substitution and Pd substitution treatment. However, not only does it lead to an increase in size, but also the efficiency of the treatment liquids to be prepared is extremely poor over many types. The method of depositing a metal such as nickel by a sputtering method and subjecting it to heat treatment to form a metal silicide not only involves a wide variety of steps, but also requires a vacuum device or the like because it is performed in a vacuum atmosphere. ,
Moreover, an annealing furnace or the like for heating is also required, which makes the apparatus considerably expensive.

The present invention has been made in view of the above circumstances, and it is possible to easily and quickly form a metal silicide containing a small amount of impurities on the surface of a substrate such as a semiconductor wafer with a smaller number of steps and a smaller footprint. It is an object of the present invention to provide a silicide forming method and an apparatus therefor.

[0008]

The invention according to claim 1 is characterized in that silicon on the surface of a substrate is brought into contact with a molten metal to alloy the metal with the silicon to form a metal silicide. Is a method of forming a silicide.

Thus, by forming a metal silicide on the surface of the substrate by a simple operation of bringing silicon on the surface of the substrate into contact with a molten metal, the number of steps can be reduced and the footprint of the device can be reduced. Can be suppressed. Moreover, a high-purity metal can be melted and used, and as a result, a metal silicide containing less impurities as compared with the plating method can be obtained.

The invention according to claim 2 is the method of forming silicide according to claim 1, wherein the contact between the silicon and the metal is performed in an inert gas atmosphere. As a result, it is possible to prevent the surface of the metal silicide from being exposed to oxygen in the air and oxidized at the time of high temperature when the substrate is pulled out from the melting furnace. As this inert gas,
Examples thereof include N ₂ gas and Ar gas.

A third aspect of the present invention is the method for forming a silicide according to the first or second aspect, wherein the metal is nickel, palladium or titanium.
Accordingly, nickel silicide (Ni _x Si _y ), palladium silicide (Pd _x Si _y ), or titanium silicide (Ti _x Si) that is optimal for use as a thermal diffusion prevention film is obtained.
_y ) can be obtained.

According to a fourth aspect of the present invention, there is provided a substrate holder for removably holding a substrate having silicon on its surface, and a melting for melting and holding a metal which forms a metal silicide by alloying with the silicon on the surface of the substrate. Silicide formation characterized by having a tank and a moving mechanism for relatively moving the substrate holder and the melting tank to bring the surface of the substrate held by the substrate holder into contact with the molten metal held in the melting tank It is a device.

The invention according to claim 5 is the silicide forming apparatus according to claim 4, further comprising a cooling device for cooling the substrate held by the substrate holder.
Accordingly, when the melting point of the molten metal is higher than that of silicon, by cooling the substrate, it is possible to prevent the silicon on the substrate surface from touching and melting the molten metal. At this time, by cooling the substrate by the cooling device so that the heat capacity for cooling the substrate by the cooling device becomes smaller than the heat capacity of the molten metal, it is possible to prevent the molten metal from contacting and solidifying the silicon.

The invention according to claim 6 is characterized in that the substrate holder and the melting tank are housed in a closed container connected to an inert gas introduction path. Is. The invention according to claim 7 is
7. The silicide forming apparatus according to claim 4, wherein the metal is nickel, palladium or titanium.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following example, nickel is used as a metal for silicidation, and a nickel silicide (N
i _x Si _y ) is formed,
Palladium silicide (Pd _x Si _y ) is formed by using palladium as the silicidizing metal,
Titanium may be used to form titanium silicide (Ti _x Si _y ).

1 to 3 show a silicide forming apparatus according to an embodiment of the present invention. This silicide forming device
A substrate W having a surface on which silicon 10 (see FIG. 4) is formed, or a substrate holder 40 that detachably holds a substrate with exposed silicon on the surface downward (face down);
Inside, a metal for alloying with silicon to form a metal silicide, in this example, a melting tank 44 holding a molten nickel 42 in which nickel is melted is provided above and below. Then, the substrate holder 40 and the melting tank 44 are formed into a closed container 46.
The sealed container 46 is housed in the inside of the container, and the closed container 46 is provided with an inert gas supply source 4 for supplying an inert gas such as N ₂ gas or Ar gas.
8 is connected to an inert gas introducing passage 50, which allows the inside of the closed container 46 to be replaced with an inert gas atmosphere.

On the lower surface of the peripheral portion of the substrate holder 40, the substrate W
A chuck ring 52 for a vacuum chuck for sucking and holding is attached. The chuck ring 52 is provided with a recess 52a that opens downward, and a vacuum path 58 extending from a vacuum source 54 is connected to the recess 52a. As a result, as shown in FIGS. 2 and 3, the substrate W held by the robot hand 56 with its surface facing downward is placed on the substrate holder 4
0, the robot hand 56 is lifted to bring the chuck ring 52 into contact with the peripheral edge of the substrate W, and then the recess 5 of the chuck ring 52 is passed through the vacuum source 54.
By vacuuming 2a, the substrate W is sucked and held.

In the lower part of the substrate holder 40, the coolant cooled by the cooler 60 is introduced into the coolant introducing passage 62a and the coolant discharging passage 62b.
Through one direction, the substrate holder 40
Cooling plate (cooling device) for cooling the substrate W held by
64 are provided. In this example, the melting point of nickel is 1453 ° C. and the melting point of silicon is 1414 ° C. Therefore, when the melting point of the molten metal (nickel) is higher than the melting point of silicon, the substrate W is It is possible to prevent the silicon 10 (see FIG. 4) on the surface of the substrate W from touching and melting the molten nickel 42 by cooling. At this time, the substrate W is cooled by the cooling plate 64 so that the heat capacity for cooling the substrate by the cooling plate 64 becomes smaller than the heat capacity of the molten nickel 42, thereby preventing the molten nickel 42 from contacting silicon and solidifying. You can Further, the substrate holder 40 is configured to be vertically movable via a vertical movement mechanism (not shown) and rotatable via a rotation mechanism.

The melting tank 44 is equipped with a heater 66 for heating the molten nickel 42 held therein to a temperature above its melting point. Here, the melting tank 44 is made of a material having a melting point higher than that of nickel, for example, a melting point 2015.
It is made of alumina at .degree. C., so that the molten nickel 42 is stably held. Similarly, the chuck ring 52 is also made of, for example, alumina so that it does not melt when it comes into contact with the molten nickel 42.

Next, an example of forming metal (nickel) silicide using this silicide forming apparatus will be described. First, for example, high-purity nickel is placed inside the melting tank 44 and heated by the heater 66 to melt the nickel, so that the melting tank 44 is filled with the molten nickel 42.
Then, as shown in FIG. 4A, the substrate W having the surface on which the silicon 10 is deposited or the substrate having the silicon exposed on the surface is held by the robot hand 56 or the like and placed in the closed container 46, and the rising position is set. The substrate holder 40 at the position is sucked and held downward. In this state, the hermetically-sealed container 46 is hermetically sealed, and an inert gas is introduced into the hermetically-sealed container 46 to create an inert gas atmosphere such as N ₂ gas or Ar gas.

Then, the substrate W held by the substrate holder 40
Is cooled by a cooling plate 64, and the substrate W is lowered while rotating the substrate W as necessary, and at least the silicon 10 on this surface is brought into contact with the molten nickel 42. As a result, as shown in FIG. 4B, the molten nickel 42 is diffused on the surface of the substrate to instantly form the nickel silicide 14 in which the silicon 10 and nickel are alloyed.

Thus, the silicon 10 on the substrate surface is
By forming the nickel silicide 14 on the surface of the substrate W by a simple operation such as bringing it into contact with the molten nickel 42, the number of steps can be reduced and the footprint of the device can be kept small. Moreover, high-purity nickel can be used by melting it,
Nickel silicide with less impurities than plating method 1
4 can be obtained.

In this way, after the nickel silicide 14 is formed on the surface of the substrate W, the substrate holder 40 is raised and the substrate W is lifted from the melting bath 44. At this time, by making the closed container 46 in an inert gas atmosphere, it is possible to prevent the surface of the high temperature nickel silicide 14 from being oxidized by oxygen in the air. Then, after the rotation of the substrate W is stopped and the substrate W is cooled to a predetermined temperature,
The substrate W is taken out of the closed container 46 by the robot hand 56 or the like, and transferred to the next step.

FIG. 5 shows the overall structure of a substrate processing apparatus equipped with the silicide forming apparatus. This substrate processing apparatus is
A load / unload unit 70 for mounting a cassette containing a substrate, a pretreatment unit 72 for performing pretreatment such as cleaning, a silicide forming device (metal melting unit) 74 shown in FIGS. A transfer robot 76 for transferring the substrate is provided therebetween.

In this apparatus, the transfer robot 76 takes out the substrates one by one from the load / unload unit 70 and transfers them to the pretreatment unit 72, and the pretreatment unit 72 performs pretreatment such as cleaning of the substrate W. I do. Then, the preprocessed substrate is conveyed to the silicide forming device 74, and at least the silicon on the surface is brought into contact with the molten nickel 42 (see FIG. 1) in the same manner as described above, whereby the nickel silicide 14 is formed on the surface of the substrate. (See FIG. 4). After that, the substrate on which the nickel silicide 14 is formed is returned to the cassette of the load / unload unit 70 by the transfer robot 76.

According to this substrate processing apparatus, in the conventional substrate processing apparatus in which nickel silicide is formed on the surface of the substrate by the solid-phase reaction method using electroless plating,
What was required in 4 steps and 4 tanks can be done in 2 steps and 2 tanks.

[0027]

As described above, according to the present invention,
Therefore, the number of steps can be reduced, and therefore, the metal silicide can be easily and inexpensively formed on the substrate surface with a smaller footprint. Moreover, by melting a high-purity metal, it is possible to obtain a metal silicide containing less impurities as compared with the plating method.

[Brief description of drawings]

FIG. 1 is a schematic view showing an entire silicide forming device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a state when the substrate is handed over from the robot hand to the substrate holder.

FIG. 3 is an enlarged view of a main part of FIG.

4A to 4D are diagrams showing an example of forming a metal silicide by the silicide forming apparatus shown in FIG.

5 is an overall layout view of a substrate processing apparatus including the silicide forming apparatus shown in FIG.

FIG. 6 is a diagram showing an example of forming a conventional metal silicide in the order of steps.

FIG. 7 is an overall layout diagram of a substrate processing apparatus in which a metal silicide is formed on the surface of a substrate by a solid-phase reaction method using conventional electroless plating.

[Explanation of symbols]

10 Silicon 14 Nickel silicide 40 substrate holder 42 Molten nickel (molten metal) 44 melting tank 46 closed container 48 Inert gas supply source 50 Inert gas introduction path 52 Chuck ring 54 Vacuum source 56 robot hand 58 vacuum path 60 cooler 64 Cooling plate (cooling device) 66 heater 74 Silicide forming equipment W board

Claims (7)

[Claims] 1. A method of forming a silicide, which comprises contacting silicon on a surface of a substrate with a molten metal to alloy the metal with the silicon to form a metal silicide. 2. The method for forming a silicide according to claim 1, wherein the contact between the silicon and the metal is performed in an inert gas atmosphere. 3. The silicide forming method according to claim 1, wherein the metal is nickel, palladium or titanium. 4. A substrate holder that detachably holds a substrate having silicon on its surface, a melting tank that melts and holds a metal that forms a metal silicide by alloying with silicon on the surface of the substrate, and the substrate holder. A silicide forming apparatus, comprising: a moving mechanism that moves the melting tank relatively to bring the surface of the substrate held by the substrate holder into contact with the molten metal held in the melting tank. 5. The silicide forming apparatus according to claim 4, further comprising a cooling device that cools the substrate held by the substrate holder. 6. The silicide forming apparatus according to claim 4, wherein the substrate holder and the melting tank are housed in a closed container connected to an inert gas introducing passage. 7. The silicide forming apparatus according to claim 4, wherein the metal is nickel, palladium or titanium.