Substrate detecting method and device

Details Substrate detecting method and device Substrate detecting method and device

2001-01-24

2003-11-04

Glick, Edward J. (Department: 2882)

Radiant energy

Photocells; circuits and apparatus

With circuit for evaluating a web, strand, strip, or sheet

C250S559360, C414S936000, C414S937000

Reexamination Certificate

active

06642533

ABSTRACT:

BACKGROUND OF THE INVENTION
The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2000-015968, filed on Jan. 25, 2000, the contents of which is herein expressly incorporated by reference in its entirety.
1. Technical Field of the Invention
The present invention relates to a method and a device for detecting substrates accommodated and transferred in a sealed container in the manufacture of thin film devices or magnetic heads that constitute semiconductor elements, liquid display panels, solar cells, and the like.
More particularly, the present invention relates to such systems enabling detection of the presence and position of each of a plurality of substrates, to which thin film forming processes are to be performed, within the sealed container. Throughout this disclosure, the term “substrate” will be used for purposes of consistency to refer to planar substrates such as silicon wafers and glass flat panes, but it will be understood that it is intended to be used in the broad context so as to be applicable to all substrates.
2. Description of Related Art
Vigorous efforts are being made to enable more precise, accelerated processes for substrates of larger size, for cost effective, high-yielding and profitable manufacturing of thin film devices. While stringent control of particulate contamination is imperative for further miniaturization of thin film devices, it is not desirable that “clean rooms” be established with a large, complex design, because the equipment cost will rise accordingly. For that reason, it has been known to employ a sealed container or pod for maintaining substrates such as wafers fairly clean within a substantially particle free environment and for storing and transferring the substrates in a sealed condition from one to another of various processing stations in a substrate transfer system generally referred to as a “mini-environment”. More recently, these containers are of the FOUP (Front Opening Unified Pod) design intended to carry semiconductor wafers sized to a diameter of 300 mm. The substrate transfer system using such FOUP type containers, wherein only the interior of the containers are maintained particle free, is fairly advantageous because it does not require a bulky clean room, while being able to transfer the wafers in a highly clean environment.
The sealed container of the FOUP design has in its interior a desired number of rack members for supporting the wafers generally horizontally, in a generally vertically spaced relationship. When the sealed container is moved to a predetermined position within a film forming apparatus, its front door is opened, and prior to the removal of the substrates therein, sensors inform whether each of the substrates is present, and whether the substrates are properly positioned in their respective rack members. This detection of the presence and position of substrates is conducted for the purpose of accommodating the substrates properly back in their original places and positions after a film forming operation has been performed to the substrates.
The sealed containers of the FOUP design are typically provided as two standard sizes: a smaller size that holds thirteen wafers and a larger size that holds twenty-five wafers. In a processing system, several such FOUP type sealed containers are loaded in a predetermined positional relationship with a film forming apparatus.
With reference to
FIG. 4
, when the sealed containers
1
are brought in a parallel arrangement with each other at predetermined locations, their front doors (not shown) are horizontally moved toward the film forming apparatus (not shown) side by means of a door removing mechanism (not shown) generally referred to as a “FOUP front opener”, whereby the containers
1
are opened to provide access to the interior thereof. A wafer handling robot
4
that faces the sealed containers
1
holds wafers
2
with its blades
3
and transfers them into a film forming station, as well as brings back the processed wafers
2
and stores them in their original places and positions within the container
1
. The wafer handling robot
4
is moved along transfer rails
7
and brought to a position facing one of the sealed containers
1
of which front door has just been opened.
The sensing of substrates within the sealed container was conventionally accomplished in such a manner as described below. A reflection sensor
9
is attached on the opposite side of the blade
3
of the wafer handling robot
4
, and when the wafer handling robot
4
is positioned in front of the opening of the sealed container
1
, the blade
3
is rotated at 180 degrees by operating a plurality of (four in the illustrated example) arms
8
of a link mechanism, so that the reflection sensor
9
faces the opening of the sealed container
1
as shown in the drawing. The wafer handling robot
4
is designed to be capable of positioning the reflection sensor
9
in relation to each of the wafers
2
within the container
1
, using the arms
8
. The reflection sensor
9
is first positioned so as to face an uppermost wafer
2
in the container
1
.
In this state, a detection circuit built in the wafer handling robot
4
activates the reflection sensor
9
, and determines the presence of the wafer
2
in its rack member based on the result whether a spot light projected from the reflection sensor has been reflected by the wafer. The wafer handling robot
4
is lowered intermittently in a certain pitch space corresponding to the intervals between the vertically spaced rack members in the container
1
, and detects the presence of the wafers
2
in each of the rack members in succession from top to bottom. When the wafer handling robot
4
has completed its detecting operation, it rotates its arms
8
at 180 degrees so that the wafer transfer blade
3
faces the wafers
2
, and rises to a position where the wafer transfer blade
3
comes opposite the uppermost wafer
2
in the container
1
, after which the wafer
2
is removed from the container and carried toward a processing system.
As described above, according to the conventional substrate detecting method, the wafer handling robot
4
, which is intended to be used for inserting and removing substrates to/from the container
1
, is doubled as the means for detecting the substrates. There is normally provided only one such wafer handling robot
4
in a processing system, where there are often a plurality of sealed containers
1
located in their respective predetermined positions. Therefore, until after all of the wafers
2
in one container have been inserted or removed to/from the container, detection of wafers
2
in other containers cannot be commenced. Life of the entire substrate handling system is shortened because the wafer handling robot
4
cannot withstand the demanding work for the both purposes of transferring and detecting the substrates. With such substrate transfer system with only one wafer handling robot, when a large number of containers
1
are provided, the transferring efficiency of substrates becomes extremely low, and troubles are more likely to occur. Furthermore, defects may be formed on thin films on the substrates due to dust which is attributable to the rough use of the substrate handling system.
Also, in order to make the wafer handling robot
4
double as the means for detecting substrates in addition to its intended use for transferring substrates, it is necessary to provide a large number of drive shafts and other mechanisms to the robot for enabling complex movements, for which its internal structure becomes complex, the cost high, and the reliability low.
Another problem is that the reflection sensors sometimes make an error especially when the rack members in the container
1
are out of position even slightly because of a dimensional error. For sensing thin substrates such as wafers, reflection sensors of limited reflection type are used, in which a spot light of extremely small diameter is projected from the reflection sensor, so that wafers opposite and

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