Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Physical stress responsive
Reexamination Certificate
1999-01-28
2001-10-02
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Physical stress responsive
C438S051000, C438S052000, C438S127000, C438S761000, C438S780000
Reexamination Certificate
active
06297069
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a micro-electronic device and an associated intermediate device assembly. In particular, the method provides support to mechanical members of a micro-electronic substrate such that microfabrication operations can be performed on the micro-electronic substrate without risk of fracture of the mechanical members.
BACKGROUND OF THE INVENTION
In the past few years, many micro-mechanical and micro-electromechanical devices (hereinafter collectively referred to as “MEMS devices”) that include mechanical members have been fabricated from silicon or other etchable materials. These MEMS devices are advantageous because they can be made with microfabrication techniques having increased precision, allow for smaller miniaturization, and are generally lighter in weight.
The proliferation of MEMS devices having members comprised of silicon or other etchable materials has been mainly facilitated by the development of microfabrication techniques for the manufacture of integrated circuit chips. Specifically, the use of thin film processes has allowed the production of MEMS devices with submicron dimensional control. For example, micro-machines such as solid state laser and fiber optic couplings, ink jet nozzles and charge plates, gyroscopes and rotating plates, magnetic disks read/write heads, and optical recording heads can now be manufactured using silicon or other etchable materials. This use of etchable materials in manufacturing has allowed these micro-machines to be made smaller and more lightweight and with greater precision.
Although the production of MEMS devices having etched mechanical members has been expanding, several manufacturing problems have not yet been adequately addressed. For instance, unlike metallic materials, silicon and other etchable materials are generally more fragile. This characteristic of silicon and other etchable materials makes them more susceptible to fracture, especially during the manufacturing process. The delicate nature of silicon and other etchable materials is exacerbated by the fact that some MEMS devices include bladders or membranes or other mechanical members that are generally very thin. The thinness of these mechanical members coupled with the fragility of the etchable material from which they are made makes these mechanical members susceptible to fracture during the manufacturing process.
In many applications, significant processing is performed on the mechanical members. For instance, in some applications, conductive contact pads or traces are formed on the various surfaces of the micro-electronic substrate including the surface of any membrane or other mechanical member. The forming of these conductive pads or traces can subject the thin bladders, membranes or other mechanical members of the micro-electronic substrate to significant forces which may sometimes damage the membrane or other mechanical members. As such, a method is needed for manufacturing a MEMS device that includes mechanical members made of silicon or other etchable materials, which will allow for subsequent processing of the MEMS device without fear of fracturing or otherwise damaging the mechanical members.
Current techniques for manufacturing MEMS devices from silicon and other etchable materials also suffer from other problems. In this regard, many microfabrication techniques, such as photolithography, generally require a planar surface. With many current procedures for forming MEMS devices, however, a planar surface is difficult to maintain.
For instance, many etching procedures initially apply a layer of photoresist to the surface to be etched. The photoresist layer is then covered by a mask that defines regions of the photoresist that are to be exposed to light. Because light is used to expose the photoresist, it is important that the mask is in close contact with the photoresist to ensure that the pattern defined by the mask is precisely replicated upon exposure of the photoresist to light. If the photoresist layer is nonplanar, however, the mask may be have to be spaced from the photoresist layer, thereby affecting the precision to which the photoresist layer is illuminated and, in turn, developed.
One example of this problem occurs where the photoresist has been applied by use of a spinning procedure. This spinning procedure is usually accomplished by applying a desired amount of flowable photoresist on the surface of a substrate. The substrate is then rotated about an axis perpendicular to the surface of the substrate. During rotation, the flowable material is spread across the substrate by centrifugal force, and the surface of the substrate is covered with a layer of photoresist.
Although this procedure deposits a layer of photoresist on the micro-electronic substrate, the outer edges of the photoresist layer tend to define a ridge (referred to as an edge bead) due to the centrifugal force and the surface tension of the photoresist. This ridge has a greater thickness than the inner portions of the photoresist and can affect the application of the mask to the photoresist, and thereby, affect the precision of the subsequent etching procedures.
As stated previously, precise etching procedures are required for producing MEMS devices from silicon and other etchable materials. As such, a method of applying layers of material, such as photoresist, is needed that prevents the formation of ridges or edge beads on the outer edges of the material layer such that precision etching may thereafter be performed.
SUMMARY OF THE INVENTION
As set forth below, the method for applying a layer of material on a surface of a micro-electronic substrate and the associated intermediate assembly of the present invention overcome the deficiencies identified with conventional micro-electronic device manufacturing. In particular, in instances in which a MEMS device includes mechanical members, such as membranes or other structures, that require delicate handling, the method of the present invention provides a supporting structure that supports the delicate mechanical members such that the mechanical members are supported during the various etching and other manufacturing steps required to form a MEMS device. Specifically, the supporting material is formed adjacent to the membranes or other mechanical members to support the membrane or other mechanical member and to guard against fracture of the mechanical members due to flexing and other forces to which the structures are subjected during the manufacturing process.
The method and intermediate assembly of the present invention also facilitates precision etching procedures during the manufacture of the MEMS devices. For instance, the method of the present invention provides supporting material that surrounds the perimeter of the micro-electronic substrate. The supporting material is generally flush with the surface of the micro-electronic substrate such that it provides a surface that is coplanar with the surface of the micro-electronic substrate that is to be etched. This coplanar surface at least partially surrounds the perimeter of the micro-electronic substrate, and as such, provides an extended perimeter surface. When a layer of material, such as photoresist, is applied to the surface of the micro-electronic substrate and is spun to coat the surface, the material will cover the surface of the micro-electronic substrate and extend onto the surrounding surface of the supporting material. Because the photoresist extends onto the surface of the supporting material, the ridge that is formed on the edges of the spun material, due to surface tension and centrifugal force, resides on the surface of the supporting material as opposed to the surface of the micro-electronic substrate. As such, the layer of material, such as photoresist, that overlies the surface of the micro-electronic substrate is planar, and as such, promotes precision microfabrication procedures.
For example, when a mask is applied to pattern the layer of photoresist, the nonplanar ridge formed at the
Fewer William Richard
Zappella Pierino Italo
Fourson George
Fredrick Kris T.
Garcia Joannie Adelle
Honeywell Inc.
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