Rotary joint for fluid

Details Rotary joint for fluid Rotary joint for fluid

1999-06-21

2001-05-22

Browne, Lynne H. (Department: 3629)

Electrical connectors

Having retainer or passageway for fluent material

Fluent material transmission line

C451S008000, C451S287000, C451S446000

Reexamination Certificate

active

06234815

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to rotary joints for fluids, and more specifically to rotary joints which allow solid-liquid mixture fluids, including slurry fluids (such as polishing solutions for polishing the surface of a silicon wafer by a chemical mechanical polishing technique, CMP for short) and corrosive fluids, to flow through the relatively rotating components and which can be connected to a monitoring apparatus for checking the polished surface state of the silicon wafer.
2. Description of the Prior Art
An apparatus for polishing the surface of silicon wafer by CMP to which this invention relates was recently developed. The apparatus, as shown in
FIGS. 5 and 6
, comprises: a rotary table
102
that rotates horizontally; a pad shaft support block
103
which moves back and forth and up and down; a polishing pad shaft
104
which, held by the shaft support block
103
, is forced to rotate; a slurry fluid feeding and discharge passage
105
formed on the non-rotary side in the pad shaft support block
103
; a polishing solution feeding and discharge mechanism
107
connected to the slurry fluid feeding and discharge passage
105
for feeding and discharging a polishing solution
106
, for example, a KOH-containing silica slurry to which isopropyl alcohol is added; a slurry fluid feeding and discharge passage
108
on the rotary side which runs through the polishing pad shaft
104
and opens under a pad head
104
a
; and a rotary joint
111
which, installed between the pad shaft support block
103
and the polishing pad shaft
104
, connects the two slurry fluid feeding and discharge passages
105
and
108
in a way that the two passages
105
and
108
communicate with each other and are relatively rotatable.
In that surface polishing apparatus, the silicon wafer
109
is polished in this manner. First, the silicon wafer
109
is held on the rotary table
102
, surface
109
a
side up, and the polishing pad shaft
104
is moved down until the pad head
104
a
comes into contact with the wafer surface
109
a
. Then the polishing solution
106
is jetted into between the pad head
104
a
and the wafer
109
by means of positive pressure action (discharging operation of the polishing solution pump) of the feeding and discharge mechanism
107
. The polishing pad shaft
104
is rotated and moved back and forth horizontally to polish the wafer surface
109
a
. After the polishing is over, the feeding and discharge mechanism
107
is switched over to negative pressure action (suction action of the polishing solution pump) to suck and discharge the residues of the polishing solution
106
into the slurry fluid feeding and discharge passages
105
and
108
. That is, care is taken so that the residues of the polishing solution
106
in the slurry fluid feeding and discharge passages
105
and
108
may not drop on the polished surface of the wafer, and that is effected by switching the passages
105
and
108
from the positive pressure mode to the negative pressure or dry mode.
The rotary joint
111
mounted in that surface polishing apparatus is constructed as follows. A joint block mounted on the pad shaft support block
103
and a rotator assembly fixed on the polishing pad shaft
104
are connected in a manner which permits relative rotation of the two. Within the joint block is formed a first fluid passage section which is connected to the slurry fluid feeding and discharge passage
105
on the non-rotary side. On the rotary side, a second fluid passage section is formed in the rotator assembly and is connected to the slurry feeding and discharging passage
108
. A space formed between the opening ends of the two fluid passage sections is sealed by seal units placed between the relatively rotating faces of the joint block and the rotator assembly. An example of such seal is a one in which relatively rotating parts of the joint block and the rotator assembly have sealing faces to be brought into contact with and pressed against each other, or an end face contact-type mechanical seal placed therebetween.
The rotary joint
111
of such a design presents many problems. That is, the polishing solution
106
is a slurry fluid containing abrasive grains. Those abrasive grains tend to intrude into and be deposited between the sealing faces (in the case of a mechanical seal, the opposing end faces of the two seal rings), making it difficult to maintain good sealing performance for a long period. A solid-containing slurry fluid, the polishing solution
106
wears out the seal faces fast, shortening the life of the seal. In the case of a mechanical seal, because the metallic parts such as a spring to thrust one seal ring against the other seal ring are exposed in the fluid passage, the solid matter in the polishing solution
106
comes into contact with the metallic parts. As a result, the abrasive grains in the polishing solution
106
impact against and remove microscopic protrusions on the surface, thus generating metallic particles or dust. The metallic particles are adsorbed to matter in the slurry fluid, thereby generating metallic ions. In the case of a corrosive fluid, the metallic particles could be corroded. If such metallic particles and dust or particles removed from the seal faces by wear are mixed with the polishing solution
106
and blasted from the pad head
104
a
, it will naturally have undesirable effects on the polishing of the wafer surface
109
a
. The entry and deposition of abrasive grains between the seal faces, the wearing of the seal faces, and the like occur noticeably when slurry feeding and discharging passages
105
and
108
are switched over from positive pressure mode to negative pressure or dry mode as mentioned above. Especially in dry mode, the seal contact faces could be heated and subjected to seizure because of frictional heat. As the intrusion and deposition of abrasive grains, wear of sealing faces, etc. affect the sealing performance, polishing solution
106
can leak through the seal faces, contaminating the wafer surface
109
a
, or get into the bearing placed between the joint block and the rotator assembly, hindering rotation of polishing pad shaft
104
. Good polishing then becomes difficult to achieve.
In recent years, meanwhile, higher precision surface polishing has been demanded in accordance with a recent trend toward high integration. To raise the precision of polishing a wafer surface
109
a
, it is desirable to check and know the state of the wafer surface
109
a
during polishing and to control the polishing conditions including the polishing rate of the pad head
104
a
. To be specific, it is preferable to provide a pad head
104
a
with an appropriate polished surface detector
110
such as a monitor at the place indicated by the broken line in FIG.
6
. The state of the wafer surface
109
a
is checked by detector
110
in real-time so as to control the polishing conditions properly on the basis of the detected surface state. To mount such a polished surface detector
110
in the rotating member pad head
104
a
, however, it is necessary to form a wiring route from the power source unit (including a display unit such as a monitor display apparatus to show the finding detected by the polished surface condition detector
110
and an operation panel and control panel to control polishing condition) to the polished surface detector
110
through the rotary joint
111
in such a way that the electric wire will not be twisted or damaged. In the surface polishing apparatus using the aforesaid rotary joint
111
, it is impossible to form such a wiring route and to provide a pad head
104
a
with a polished surface detector
110
.
Those problems with the rotary joint
111
are encountered not only in the aforesaid surface polishing apparatus but are common to rotary equipment in which a slurry fluid-like polishing solution or a corrosive fluid has to be blown between component parts relatively rotating at a rate higher than a certain level. Such being the case, it has been str

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