Measuring module

Details Measuring module Measuring module

2002-04-11

2004-09-28

Stafira, Michael P. (Department: 2877)

Optics: measuring and testing

By polarized light examination

Of surface reflection

Reexamination Certificate

active

06798513

ABSTRACT:

FIELD OF THE INVENTION
The invention concerns a measuring module for measuring the surface of wafers with a measuring head and a measuring table, which is equipped with a wafer accommodation.
BACKGROUND OF THE INVENTION
For quality control purposes, so-called “integrated measuring technology” is increasingly used in the manufacture of semi-conductor chips, in particular for the manufacture of wafers with a diameter of 300 mm. With integrated measuring technology the measuring device, in contrast to conventional “stand-alone” measuring technology, is directly linked to and integrated into the manufacturing equipment, so as to allow quality monitoring to be performed as close to the process as possible.
The integration of measuring technology into process equipment is often associated with very high expense, since changes to both systems, or rather to the process equipment and the measuring systems, are often necessary, which, in turn, entails additional costs.
However, in 300 mm wafer technology there is a high level of standardization. The process devices are equipped with so-called “Equipment Front End Modules” (EFEM). The EFEM's represent the interface between the chip factory and the process device and provide logistics, or rather the automatic loading of the equipment with wafers. The EFEM's generally have at least two load ports, whose dimensions are standardized. The containers (Front Opening Unified Pod, FOUP) containing the wafers are stopped on the load ports. The EFEM also has a robot and is connected to the current process device on the back. The EFEM contains a wafer container (FOUP), supplies the wafers to the process device by means of a port, with the aid of another robot, and again feeds the wafers to an FOUP after the process.
In principle, an EFEM can also have several load ports. The load ports can easily be changed out. The EFEM is thus an ideally suited place for connecting a measuring device to process equipment, because in doing so the available logistics of the EFEM can be used with robots anyway to integrate the measuring procedure into the manufacturing process in a flexible way.
With the aid of integrated measuring technology it is possible to feed the wafers for measurement upon entry, prior to the process, and for final control after the process. This makes it possible to avoid any further processing of defective wafers and resupply the equipment through the process window provided if deviations in parameters are determined.
A prerequisite for attaching the measuring module to the EFEM, instead of a load port, is however that the measuring devices not be any wider or deeper than a load port, and must therefore keep to standardized dimensions.
Since, however, with most measuring procedures, the entire wafer must be examined, with its diameter of 300 mm, considerable problems arise in observing these standardized measurements.
Devices and procedures are known that do not adhere to these standardized dimensions. It is known from current technology that measuring device
1
must be installed in a stationary position and the wafer
3
in a moveable position, as shown in
FIG. 1
a
. The measuring point is indicated as
4
. This variant is quite widespread, because the measuring devices
1
are often very large and are too sensitive to be able to be moved. If an XY pathway is used, then the required surface, indicated by the frame
2
, must amount to at least 600×600 mm (see
FIG. 1
a
), so that the width of the load port is significantly exceeded.
From U.S. Pat. No. 6,181,427 the so-called “R Theta Procedure” is known, with which a translatory movement is replaced by the rotation of the wafer
3
. The measuring device
1
′, which is smaller than measuring device
1
, is translatorily moved by half of the diameter of the wafer. This does achieve a reduction in the footprint, although the minimum required surface (frame
2
′) still amounts to 300×450 mm, as shown in
FIG. 1
b
. Through the combination of a complete revolution and a translation around half of the diameter of the wafer, any point can be reached. This method allows for a significantly more compact construction, whereby the critical width of the load ports is however not exceeded, although a dimension of at least 450 mm is achieved in the depth. In practice, however, this value is higher, since there is also a footprint for the measuring device
1
′.
The problem of the invention consists of finding a measuring module with a compact construction, so that a surface area of 450×450 mm is not exceeded.
SUMMARY OF THE INVENTION
This problem is solved with a measuring module, whose measuring device comprises a measuring head equipped with a miniaturized measuring unit, and a spatially separately arranged control and evaluation unit, and that the measuring head is arranged so as to be able to slide linearly by means of a sliding drive.
By “Miniaturized Measuring Device” a device is understood, whose footprint covers <150×300 mm. Such measuring units, for example, are known from U.S. Pat. No. 5,502,567 or U.S. Pat. No. 6,091,499.
Since the control and evaluation unit is spatially arranged separately, such as under the measuring table or even outside the available surface, these components of the measuring device do not need to be moved. The measuring head can therefore be designed in a compact way and the sliding drive can accordingly be designed in a lower-performance and thus also more compact way.
The control and evaluation unit, as an example, is connected to the measuring head by means of a cable or infrared path.
Such a miniaturized measuring head offers the advantage that it not only has a small footprint, but it can also be designed to be robust through its reduction to the most necessary components. Thus a compact and reasonably priced measuring module is created, which remains within the standardized dimensions of a load port and can thus be integrated into the wafer process equipment without a problem, without any changes having to be made to the process equipment itself.
By preference, The rotation drive is a rotation motor arranged under the wafer accommodation. The immediate arrangement of the rotation motor under the accommodation saves space, since no additional footprint is therefore required.
The sliding drive by preference comprises two linear motors arranged on two opposing sides of the wafer accommodation.
By preference, both linear motors are connected to each other by a support extending over the wafer accommodation, on which the measuring head is arranged.
The measuring unit integrated into the measuring head may, for example, be a spectrometer for measuring layer thickness and composition, an FTlR spectrometer for measuring impurities, an Ellipsometer for measuring layer thickness, a microscope for measuring lateral structures, as well as defects, a scattered light measuring device for measuring particles and other defects, or an atomic force microscope.


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