US20040124090A1

US20040124090A1 - Wafer electroplating apparatus and method

Info

Publication number: US20040124090A1
Application number: US10/335,364
Authority: US
Inventors: Chen-Chung Du; Pang-Min Chiang; Chih-Cheng Wang; Jen-Rong Huang
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2002-12-30
Filing date: 2002-12-30
Publication date: 2004-07-01

Abstract

A wafer electroplating apparatus and method, comprising a wafer turning assembly, a vertical movement assembly, a wafer tilting assembly, and a frame. The wafer turning assembly has a turning shaft and a clasp for holding a wafer. The wafer tilting assembly has a tilting table being driven by a driving system, e.g. a cylinder, carrying an electroplating unit and wafer turning assembly. Thus the clasp holding a wafer and the electroplating unit are simultaneously inclined at preset angle against the horizontal plane, allowing for a large inclination angle. Therefore, gas bubbles generated during electroplating readily escape, and quality of electroplating is improved.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer electroplating apparatus and method, particularly to a wafer electroplating apparatus and method having a wafer-holding clasp and an electroplating unit that are mounted on a common tilting table, being simultaneously tilted, so that larger tilting angle can be adjusted for and gas bubbles generated during electroplating escape readily.

2. Description of Related Art

When performing conventional fountain-type electroplating of a wafer, the wafer is rotated to ensure uniform electroplating. The main difference to bath type electroplating is that a clasp holding the wafer is not completely immersed in a bath, establishing dry contact.

In fountain-type electroplating, a wafer is laid onto a electroplating tank. During the ensuing chemical reaction, gas bubbles are produced, which readily stick to a electroplating surface of the wafer, causing the chemical reaction locally to stop, so that incomplete electroplating results. To avoid this shortcoming, the wafer is inclined, allowing gas bubbles to escape easily.

Inclining of the wafer is done by turning the clasp holding the wafer by an inclination angle, so that the wafer and a fixed electroplating tank inclined against each other. This results in the wafer, e.g. a 12 inch wafer, having an increased inclined diameter and the clasp being immersed in the eletroplating solntion at an edge thereof. To avoid contamination of the clasp at a rear side thereof, the inclination angle is only chosen to be 1-2 degrees. However, a small inclination angle results in insufficient clearing of gas bubbles. On the other hand, when being turned, the clasp is partially exposed in succession to air and electroplating solution of the tank, which easily leads to external air bubbles entering the electroplating solution in the tank and impairing the chemical reaction, so that electroplating is defective.

Fountain-type electroplating requires a suitable gap between the wafer and the top of tank. Thus pressure of the electroplatong solution in the tank is maintained while liquid flows out through the electroplating tank, so that liquid completely and uniformly covers the wafer. For maintaining pressure of the electroplating solution, the cross-section area of the gap is required to be smaller than the cross-section area of an inlet of the tank, resulting in an outflow velocity of liquid that is larger than an inflow velocity thereof and in uniform flow through the gap.

While fountain-type electroplating allows for electroplating with uniform thickness, pockets of imperfect electroplating occur easily due to gas bubbles. In order to allow gas bubbles readily to escape, the wafer is inclined. This not only creates an external disturbance, but also due to an inclined orientation of the wafer and buoyancy leads to the gas bubble movement.

In conventional art, the electroplating tank is fixed, only the wafer is inclined against a horizontal plane. Since the cross-section area of the gap between the wafer and the tank is nonuniform, pressure is not maintained easily, the clasp is in turns exposed to air and liquid, resulting in external air bubbles enturing to the tank that adversely affect the chemical reaction. Furthermore, inclination of the wafer is restricted to 1-2 degrees, as described in U.S. Pat. No. 6,080,291, resulting in ineffective clearing of gas bubbles.

Moreover, the apparatuses disclosed in U.S. Pat. No. 6,080,291 and No. 6,334,937 have the following shortcomings:

1. When the wafer is inclined, with the tank unmoving, not only the cross-section area between the wafer and the tank nonuniform, but also the permissible inclination angle is reduced.

2. The clasp has no liquid blocking ring. When being held, the wafer at the rear side thereof is easily contaminated.

3. Using a robot to incline the wafer requires a higher cost.

4. No sealing device for the electroplating area is provided, so leaking of gas generated in the bath is not effectively prevented.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a wafer electroplating apparatus which allows to set large inclination angle, so that gas bubbles escape easily, and which comprises a wafer turning assembly, a vertical movement assembly, a wafer tilting assembly, and a frame, with the wafer turning assembly having a clasp and a turning shaft and the wafer tilting assembly having an electroplating unit set on a tilting table driven by a driving system, e.g., a gas pressure cylinder, so that a mounted wafer and the electroplating unit are simultaneously inclined at any preset angle.

Another object of the present invention is to provide a wafer electroplating apparatus which avoids contamination of the mounted wafer at a rear side thereof by adding a protective ring to the clasp for keeping liquid of an electroplating tank from reaching the rear side of the wafer.

A further object of the present invention is to provide a wafer electroplating apparatus which prevents gas from leaking to the outside when the wafer is tilted by having a dome set on the wafer turning assembly, keeping the wafer turning assembly sealed during vertical movements thereof.

A further object of the present invention is to provide a wafer electroplating method in which the wafer turning assembly with the clasp and the electroplating unit, set on the tilting table driven by the driving system, are simultaneously tilted, so that adjusting a mounted wafer at larger inclination angle against the horizontal plane is possible, allowing gas bubbles generated during electroplating easily to escape.

The present invention can be more fully understood by reference to the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the wafer electroplating apparatus of the present invention. [0020]
FIG. 2 is a front view of the wafer electroplating apparatus of the present invention. [0021]
FIG. 3 is a side view from the right of the wafer electroplating apparatus of the present invention. [0022]
FIG. 4 is a top view of the wafer electroplating apparatus of the present invention. [0023]
FIG. 5 is a sectional view of the wafer electroplating apparatus of the present invention. [0024]
FIG. 6 is an enlarged sectional view of the clasp of the present invention.[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. [0026] 1-4, the wafer electroplating apparatus of the present invention mainly comprises: a frame 10; a wafer turning assembly 20; a vertical movement assembly 30; and a wafer tilting assembly 40.
The [0027] frame 10 has a main body for stable mounting of other components and four lower corners to each of which a wheel 111 and an adjustable support 112 are attached, allowing either to move or to fix the frame 10. The frame 10 carries a pipe unit and a control unit.
The [0028] wafer turning assembly 20 has a casing 21. Inside the casing 21, the wafer turning assembly 20 further has a gas inlet 22, a turning shaft 23, electrical connectors 24 and a driving unit 241. A motor and a conveyor belt in the driving unit 241 drive a rotating movement of the turning shaft 23. On a lower end of the wafer turning assembly 20, a clasp 25 is provided for holding a wafer, being in turn connected with a gas pressure cylinder 26 inside the turning shaft 23. A dome 27 is set on the casing 21, covering the casing 21 tightly during electroplating process and preventing gas from leaking to the outside as well as air entering the inside of the casing 21.
The [0029] vertical movement assembly 30 has a vertical column 31 set on a tilting table 42. A movement unit 32 with ball bearings and a servomotor 33 drive a vertical movement of the wafer turning assembly 20, as in conventional art.
The [0030] wafer tilting assembly 40 is mounted on the main body 11, having a horizontal shaft 411 held in two seats 41 on two opposite sides of the main body 11. The tilting table 42 is inserted between the seats 41, turning with the horizontal shaft 411, with a lock 412 on the seat 41 fixing the tilting table 42 a tilting angle. A connecting rod 421 hingedly connects the tilting table 42 with a gas pressure rod of a gas pressure cylinder 43. The gas pressure cylinder 43 has a fixed end connected with the main body 11. The tilting table 42 carries an electroplating tank unit 44. The electroplating tank unit 44 contains an electroplating solution and has an electroplating tank 441 serving as an anode. The electroplating tank 441 has a overflow tank 442, collecting liquid overflowing from the electroplating tank 441. The overflow tank 442 is covered by the dome 27.
The [0031] gas pressure cylinder 43, via the gas pressure rod thereof, drives the tilting movement of the tilting table 42 towards a suitable tilting angle. Since the electroplating tank 441 and the clasp 25 participate simultaneously in the tilting movement, the gap remain unchanged. Thus adjusting for a large tilting angle is possible, allowing the bubble generated during electroplating of the wafer easily to escape, improving quality of electroplating.
Referring to FIG. 6, the [0032] clasp 25 has an upper part 251 and a lower part 252 effectively holding the wafer. An cathode 253 is placed in a suitable position, and a liquid blocking ring 254 is laid around a periphery of the clasp, preventing the electroplating solution from contaminating the wafer at a rear side thereof when a tilting angle is assumed.
The wafer electroplating method of the present invention comprises simultaneous tilting of the turning [0033] shaft 23 with the clasp 25 and the electroplating unit, set on the tilting table 42 that is connected with the horizontal connecting rod 411 and driven by a driving system (in the embodiment shown, the gas pressure cylinder 43). Thus adjusting a mounted wafer at larger inclination angle against the horizontal plane is possible, allowing the bubbles generated during electroplating easily to escape.
For better understanding, the steps of the wafer electroplating method of the present invention are given as follows: [0034]
A. Inserting the wafer into the clasp; B. holding the wafer in the clasp; C. lowering into the location of electroplating; D. inclining of the tilting table to incline the wafer; E. slowly turning the wafer and electroplating; F. completing of electroplating; G. raising from the location of electroplating; H. reversing inclination of the tilting table; I. fast turning of the wafer for drying; J. stopping of the wafer; K. opening the clasp; L. removing the wafer. [0035]
As the above explanation shows, the present invention offers the following advantages:[0036]
(1) A large tilting angle (over 45 degrees) is possible, allowing the gas bubbles generated during electroplating readily to escape. [0037]
(2) The tilting angle is freely adjustable, increasing flexibility. [0038]
(3) The clasp is not in turns exposed to air and liquid, so that no gas bubbles hindering chemical reactions enter the electroplating tank. [0039]
(4) Different designs of the clasp for larger wafer are not required, simplifying the assembly. [0040]
(5) Electroplating is performed in an unchanging electric field, any variation of the tilting angle does not alter the geometry of cathode, anode and the wafer.[0041]
The wafer electroplating apparatus and method of the present invention provides for a wafer-holding clasp and an electroplating unit that are mounted on a common tilting table, being simultaneously tilted, so that larger tilting angle is adjustable for and gas bubbles generated during electroplating escape readily. Thus an improved electroplating apparatus and method are provided, providing for various practical functions. [0042]
While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims. [0043]

Claims

1. A wafer electroplating method, comprising the steps of:

A. inserting a wafer into a clasp;

B. holding said wafer in said clasp;

C. lowering said wafer to a location of electroplating;

D. inclining of a tilting table to incline said wafer;

E. slowly turning said wafer and electroplating;

F. completing of electroplating;

G. raising said wafer from said location of electroplating;

H. reversing inclination of said tilting table;

I. fast turning of said wafer for drying;

J. stopping of said wafer;

K. opening said clasp; and

L. removing said wafer.

2. A wafer electroplating apparatus, comprising:

a frame, having a main body, on which a piping system and a control unit are installed;

a wafer turning assembly, having a casing and a lower end, to which a clasp for holding a wafer is attached;

a vertical movement assembly, mounted on a side of said wafer turning assembly, having a vertical column, on which a vertical driving device is installed, driving said wafer turning device in a vertical movement; and

a wafer tilting assembly, having two seats, which are fastened on two opposite sides of said main body, with a tilting table inserted between and held by said two seats, said tilting table being inclined at a tilting angle, as driven by a driving system via a connecting rod, said tilting table carrying said vertical shifting assembly and an electroplating unit;

wherein a suitable value of said tilting angle is set using said driving system, with said clasp and said electroplating unit being simultaneously tilted and, by tilting to any angles, the clearance between the two is kept constant, thereby not hindering fluid patent be changed. The tilting angle of the wafer can be tilted to a larger angles. Gas bubbles generated during electroplating of said wafer is readily to escape from surface.

3. The wafer electroplating apparatus according to claim 2, wherein said wafer turning assembly further comprises a gas inlet, a turning shaft, electrical connectors and a driving unit, with a gas pressure cylinder being installed inside said turning shaft, holding said clasp.

4. The wafer electroplating apparatus according to claim 2, wherein said clasp has a cathode at a suitable position and a liquid blocking ring.