JPH1180968A - Plating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plating apparatus capable of efficiently and uniformly packing a material, such as copper or copper alloy, of a small specific electric resistance into fine recesses, such as grooves, for fine wiring. SOLUTION: This plating apparatus has a plating tank 10 which holds a plating liquid, a holding table 14 which holds a substrate W within this plating tank 10, an ultrasonic vibrator transducer 16 which forms standing waves with the wall surface of the plating tank 10 by generating ultrasonic vibration nearly parallel on the surface to be treated of the substrate W in the plating liquid in the plating tank 10 and a moving means 36 which moves this holding table 14 along the surface to be treated of the substrate W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating apparatus for a substrate, and more particularly to a plating apparatus for filling a wiring groove or the like formed in a semiconductor substrate with a metal such as copper (Cu).

[0002]

2. Description of the Related Art Conventionally, in order to form a wiring circuit on a semiconductor substrate, a film is formed on the substrate surface by sputtering or the like, and then the film is formed by chemical dry etching using a pattern mask such as a resist. Unnecessary parts were removed.

[0003] Materials for forming a wiring circuit include:
Aluminum (Al) or aluminum alloy is used, but as the degree of integration increases, the wiring becomes thinner,
The increase in current density causes thermal stress and temperature rise.
This becomes more remarkable as Al or the like is diluted by stress migration or electromigration, and eventually there is a risk of disconnection.

Therefore, in order to avoid excessive heat generation due to energization, it is necessary to employ a material having higher conductivity for forming the wiring. Among the current materials, copper (Cu) and silver (Ag) are materials having lower electric resistivity than Al-based materials.

[0005] However, it is difficult to dry-etch Cu or its alloy, and it is difficult to employ the above-described method of forming a pattern after forming the entire surface. Therefore, a process of forming a wiring groove in a predetermined pattern in advance and filling the groove with Cu or an alloy thereof may be considered. According to this, a step of removing the film by etching is unnecessary, and a polishing step for removing a surface step may be performed if necessary. Further, there is an advantage that a portion called a plug that connects the upper and lower sides of the multilayer circuit can be formed at the same time.

[0006]

However, the shape of such a wiring groove or plug has a considerably high aspect ratio (ratio of depth to diameter or width) as the wiring width becomes finer. It was difficult to uniformly fill the metal. In addition, a vapor phase growth (CVD) method is used as a film forming means of various materials. However, it is difficult to prepare an appropriate gaseous raw material using Cu or an alloy thereof. However, there is a problem that carbon (C) is mixed into the deposited film to increase the migration property.

Further, a method has been proposed in which a substrate is immersed in a plating solution to perform electroless or electrolytic plating.
Insufficient circulation of liquid and supply of ions to the bottom of the groove or hole, resulting in slower film growth at the bottom than at the edge of the groove, resulting in a clogging of the top of the groove and a void at the bottom. For example, uniform filling was difficult.

[0008] In view of the above-mentioned circumstances, the present invention provides a plating method capable of efficiently and uniformly filling a material having a small electric resistivity such as copper or a copper alloy into a fine depression such as a fine wiring groove. It is intended to provide a device.

[0009]

According to a first aspect of the present invention, there is provided a plating tank for holding a plating solution, a holding table for holding a substrate in the plating tank, and the plating tank in the plating tank. Generating an ultrasonic vibration substantially parallel to the surface to be processed, and an ultrasonic oscillator for forming a standing wave between the wall surfaces of the plating tank, and moving the holding table along the surface to be processed of the substrate. And a moving device.

Thus, the ultrasonic vibrator is, for example, 1
When operating at a frequency of 10 Hz to 10 MHz and applying ultrasonic vibrations to the plating solution, between the ultrasonic vibrator and the side wall facing, the plating solution positioned on the upper surface of the substrate is parallel to the substrate. A standing wave of a propagating compression wave is formed. At the position corresponding to the antinode of the standing wave, a large compressional wave is formed with a large amplitude, and the resulting pressure fluctuation promotes the flow and replacement of the plating solution in the groove of the substrate, thereby performing good plating in the groove. Since the position of the antinode of the standing wave moves evenly to each part on the substrate by the movement of the substrate by the moving means, the plating speed in the groove of each part of the substrate can be uniformly improved. The plating method may be electrolytic plating or electroless plating.

The invention according to claim 2 is the plating apparatus according to claim 1, wherein the moving means rotates the holding table. Non-uniform plating speed can be avoided by a relatively simple method.

The invention according to claim 3 is the plating apparatus according to claim 1, wherein the holding table is provided with heating means for heating the substrate. For example,
By heating the semiconductor wafer to around 100 ° C., the mass transfer near the wafer surface is promoted by improving the material diffusivity and decreasing the viscosity.

According to a fourth aspect of the present invention, there is provided the plating apparatus according to the first aspect, wherein the holding table is vibrated up and down. Thus, the effect of promoting the flow of the plating solution into the fine grooves by the ultrasonic vibration is further enhanced, and the efficiency of plating adhesion to these is improved.

According to a fifth aspect of the present invention, after plating using the plating apparatus according to any one of the first to fourth aspects, an unnecessary portion of the metal adhered to the substrate is polished by a chemical / mechanical polishing apparatus. And removing the substrate.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. This plating apparatus includes a plating tank 10 formed as a substantially rectangular parallelepiped container by four side walls 10a, 10b, 10c, 10d and a bottom plate 10e.
And a rotatable holding table 14 supported by a shaft 12 penetrating through the bottom plate 10e, and one side wall 10 of the plating tank 10.
and an ultrasonic vibrator 16 that generates ultrasonic vibration toward the opposing side wall 10c. A seal mechanism 20 is provided at the bottom plate penetration portion 18 of the shaft body 12 to prevent the plating solution from leaking.

A fixing ring 24 for fixing the substrate W in a liquid-tight manner via a seal ring 22 is attached to the upper portion of the holding table 14 so that the plating solution does not turn to the back side of the holding table 14.
A cavity 28 for accommodating the heater 26 is formed inside the holding table 14, and this cavity 28 communicates with a hollow portion 30 of the shaft 12 in which a power supply cable to the heater 26 is arranged. The shaft body 12 is connected to a motor 36 for rotational driving via a pulley 32 and a pulley belt 34, and rotates at a controlled rotation speed. The shaft body 12 is also provided with a vibration mechanism 38 for vibrating the shaft body 12 up and down.

The plating bath 10 is provided with a plating solution flow path (not shown) for keeping the concentration and temperature of the plating solution constant. Route is provided.

The operation of the plating apparatus configured as above will be described for the case of plating Cu or an alloy thereof for forming a wiring circuit on a semiconductor substrate. As shown in FIG. 3A, a substrate W to be processed includes a conductive layer 52 and SiO ₂ on a semiconductor substrate 50 on which a semiconductor element is formed.
After depositing an insulating layer 54 made of Ti, a contact hole 56 and a trench 58 for wiring are formed by lithography and etching technology, and a barrier layer 6 made of TiN or the like is formed thereon.
0 is formed.

The substrate W is placed on the holding table 14, and
This is maintained at a predetermined temperature close to 100 ° C. by the heater 26 to promote the diffusion of the substance in the plating solution on the substrate surface and to lower the viscosity of the plating solution. Further, the plating solution in the plating tank 10 is also maintained at a predetermined temperature. Then, the ultrasonic vibrator 16 is operated at a frequency of, for example, 1 Hz to 10 MHz to apply ultrasonic vibration to the plating solution. Further, the motor 36 is driven to move the holding table 14 to, for example,
The holder 14 is rotated at a rotation speed of about pm, and furthermore, the vibrating mechanism 38 is operated to move the holding table 14 up and down at a cycle of about 1-3 times per rotation.

The oscillation of the ultrasonic vibrator 16 causes the plating solution located on the upper surface of the substrate W to move in a direction parallel to the substrate W between the ultrasonic vibrator 16 and the side wall 10c facing the ultrasonic vibrator 16 as shown in FIG. A standing wave of a propagating compression wave is formed. As a result, a large compression wave amplitude is formed at the position corresponding to the antinode of the standing wave, and a large pressure fluctuation occurs with the compression wave. Plating is performed. The plating efficiency is
The vibration is also promoted by the vertical vibration of the holding table 14, that is, the substrate W by the vibration mechanism 38.

On the other hand, at the position of the node of the standing wave, such a pressure fluctuation is small, so that the plating is not promoted. However, since the position of the antinode of the standing wave moves evenly to each part on the substrate W by the rotation of the holding table 14, the plating speed in the groove is improved due to the bias of the antinode of the standing wave. Non-uniformities are avoided. The movement of the holding table 14 may be an operation of reciprocating in the traveling direction of the ultrasonic wave.

By the above liquid phase plating process, FIG.
As shown in FIG. 5, the contact hole 56 and the groove 58 of the semiconductor substrate W are filled with Cu, and the Cu
Layer 62 is deposited. After that, chemical mechanical polishing (CM
By P), the Cu layer on the insulating film 54 is removed to make the surface of the Cu layer 62 filled in the contact hole 56 and the wiring groove 58 substantially flush with the surface of the insulating film 54. As a result, a wiring made of the Cu layer 62 is formed as shown in FIG.

[0023]

As described above, according to the present invention,
Due to the pressure fluctuation formed in the plating solution by the ultrasonic vibrator, the flow and replacement of the plating solution in the groove of the substrate are promoted,
By the movement of the substrate by the moving means, the plating speed in the groove of each part of the substrate can be uniformly improved. Therefore, a material having a small electric resistivity such as copper or a copper alloy can be efficiently and uniformly filled in a fine recess such as a fine wiring groove, and therefore, a semiconductor integrated circuit having a high density can be used. It is possible to provide a useful technique for promoting the conversion.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an entire plating apparatus according to an embodiment of the present invention.

2 (a) is a plan view and FIG. 2 (b) is a side view for explaining the operation of the plating apparatus according to the embodiment of FIG.

FIG. 3 is a cross-sectional view illustrating an example of a step of performing plating by the plating apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Plating tank 10a, 10b, 10c, 10d Side wall 10e Bottom plate 12 Shaft 14 Holding table 16 Ultrasonic vibrator 18 Bottom plate penetration part 20 Seal mechanism 22 Seal ring 24 Fixed ring 26 Heater 28 Cavity 30 Hollow part 32 Pulley 34 Pulley belt 36 Motor 38 Vibration device 54 Insulating film 56 Contact hole 58 Groove 62 Cu layer W Substrate

Claims (5)

[Claims] 1. A plating tank for holding a plating solution, a holding table for holding a substrate in the plating tank, and an ultrasonic vibration generated in the plating bath in the plating solution substantially parallel to a surface to be processed of the substrate. A plating apparatus comprising: an ultrasonic vibrator that forms a standing wave between wall surfaces of a plating tank; and a moving unit that moves the holding table along a surface to be processed of the substrate. 2. The plating apparatus according to claim 1, wherein the moving means rotates the holding table. 3. The plating apparatus according to claim 1, wherein said holding table is provided with a heating means for heating said substrate. 4. The plating apparatus according to claim 1, further comprising a vibration device that vibrates the holding table up and down. 5. After plating using the plating apparatus according to claim 1, unnecessary portions of the metal adhered to the substrate are removed by polishing with a chemical / mechanical polishing apparatus. Substrate processing method.