Patent Application
20050255666
The present invention relates generally to bonding techniques. More particularly, the invention includes a method and structure for bonding substrates together using alignment marks. Merely by way of example, the invention has been applied to integrating a mechanical based structure with an integrated circuit chip. But it would be recognized that the invention has a much broader range of applicability.
Visual display technologies have rapidly developed over the years. Most particularly, electronic displays for outputting television shows, streaming video, and the like. From the early days, cathode ray tube technology, commonly called CRTs, outputted selected pixel elements onto a glass screen in conventional television sets. These television sets originally output black and white moving pictures. Color television sets soon replaced most if not all black and white television units. Although very successful, CRTs were often bulky, difficult to make larger, and had other limitations.
CRTs were soon replaced, at least in part, with liquid crystal panel displays. These liquid crystal panel displays commonly called LCDs used an array of transistor elements coupled to a liquid crystal material and color filter to output moving pictures in color. Many computer terminals and smaller display devices often relied upon LCDs to output video, text, and other visual features. Unfortunately, liquid crystal panels often had low yields and were difficult to scale up to larger sizes. These LCDs were often unsuitable for larger displays often required for television sets and the like.
Accordingly, projection display units have been developed. These projection display units include, among others, a counterpart liquid crystal display, which outputs light from selected pixel elements through a lens to a larger display to create moving pictures, text, and other visual images. Another technology is called “Digital Light Processing” (DLP), which is a commercial name from Texas Instruments Incorporated (TI) of Texas, USA. DLP is often referred to as the use of “micro-mirrors.” DLP relies upon a few hundred thousand tiny mirrors, which line up in 800 rows of 600 mirrors each. Each of the mirrors is hinged. An actuator is attached to each of the hinges. The actuator is often electrostatic energy that can tilt each of the mirrors at high frequency. The moving mirrors can modulate light, which can be transmitted through a lens and then displayed on a screen. Although DLP has been successful, it is often difficult to manufacture and subject to low yields, etc. DLP is also manufactured using MEMS based processing techniques. Such MEMS based processing technique is often costly and difficult to scale up for efficient processing.
From the above, it is seen that an improved technique for processing devices is desired.
According to the present invention, techniques for bonding substrates are provided. More particularly, the invention includes a method and structure for bonding substrates together using alignment marks. Merely by way of example, the invention has been applied to integrating a mechanical based structure with an integrated circuit chip. But it would be recognized that the invention has a much broader range of applicability.
In a specific embodiment, the invention provides a method for bonding substrates together. The method includes providing a first substrate comprising a first surface. The first substrate comprises a plurality of first chips thereon. Each of the chips has integrated circuit devices. The first substrate includes a first alignment mark on the first substrate and a second alignment mark on the first substrate. The method also includes providing a second substrate comprising a silicon bearing material and second surface. The second substrate comprising a plurality of second chips thereon. Each of the chips comprises a plurality of mechanical structures. The second substrate has a first silicon based pattern on the second substrate and a second silicon based pattern on the second substrate. The method includes moving the first alignment mark of the first substrate to the first silicon based pattern on the second substrate and aligning the second alignment mark of the first substrate to the second silicon based pattern on the second substrate. A portion of at least one of the first substrate or the second substrate is illuminated with electromagnetic radiation. The method includes detecting a portion of the electromagnetic radiation and using the detected portion of the electromagnetic radiation to align the first substrate with the second substrate. The method also includes coupling the first substrate with the second substrate by contacting the first surface with the second surface and bonding the first surface with the second surface. Preferably, the method holds the first substrate with a first vacuum chuck to substantially contact a backside of the first substrate to the first vacuum chuck and holds the second substrate with a second vacuum chuck to substantially contact a backside of the second substrate to the second vacuum chuck.
In an alternative specific embodiment, the invention provides a method for bonding different substrates together to manufacture display devices for visual imaging applications. The method includes providing a first substrate comprising a first surface, the first substrate comprising a plurality of first chips thereon. Each of the chips comprises integrated circuit devices. Preferably, the first substrate comprises a first alignment mark on the first substrate and a second alignment mark on the first substrate. The method also includes providing a second substrate comprising a silicon bearing material and second surface. The second substrate comprises a plurality of second chips thereon. Each of the chips comprising a plurality of mechanical mirror structures. The second substrate comprises a first silicon based pattern on the second substrate and a second silicon based pattern on the second substrate. The method includes moving the first alignment mark of the first substrate to the first silicon based pattern on the second substrate and moving the second alignment mark of the first substrate to the second silicon based pattern on the second substrate. The method maintains substantial parallel alignment between the first surface and the second surface during a portion of time associated with moving the first alignment mark to the first silicon based pattern and moving the second alignment mark with the second silicon based pattern. The method illuminates a portion of at least one of the first substrate or the second substrate with electromagnetic radiation while the first surface is in substantial parallel alignment with the second substrate. The method also detects a signal associated with a portion of the electromagnetic radiation and uses the signal associated with the detected portion of the electromagnetic radiation to align the first substrate with the second substrate using at least the first alignment mark and the first silicon based pattern or the second alignment mark and the second silicon based pattern. The method couples the first substrate with the second substrate by contacting the first surface with the second surface. Next, the method initiates a bond between the first surface with the second surface.
Many benefits are achieved by way of the present invention over conventional techniques. For example, the present technique provides an easy to use process that relies upon conventional technology. In some embodiments, the method provides higher device yields for the bonded substrates. Additionally, the method provides a process that is compatible with conventional process technology without substantial modifications to conventional equipment and processes. Preferably, the invention provides for an improved integrated structure including integrated circuits and mirror structures for display applications. Preferably, infrared radiation (IR) is used to allow for improved alignment accuracy and may include other benefits. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below.
Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow.
According to the present invention, techniques for bonding substrates are provided. More particularly, the invention includes a method and structure for bonding substrates together using alignment marks. Merely by way of example, the invention has been applied to integrating a mechanical based structure with an integrated circuit chip. But it would be recognized that the invention has a much broader range of applicability.
A method for bonding a pair of substrates together according to an embodiment of the present invention may be outlined as follows:
The above sequence of steps provides a method for bonding a pair of substrates together according to an embodiment of the present invention. As shown, the method uses a combination of steps including a way of bonding two substrates of different type together for a display device having a plurality of movable mirror structures. Other alternatives can also be provided where steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein. Further details of the present method can be found throughout the present specification and more particularly below.
The method also includes providing a second substrate 105 comprising a silicon bearing material and second surface 115. Preferably, the second substrate is a silicon wafer or silicon on insulator wafer. The second substrate comprises a plurality of second chips thereon. Each of the chips comprising a plurality of mechanical mirror structures. The second substrate comprises a first silicon based pattern 119 on the second substrate and a second silicon based pattern on the second substrate. Preferably, each of the substrates has a polished face side that has been polished using chemical mechanical polishing, chemical smoothing, and/or other techniques. Other than silicon based substrates, other substrates can also be used. These substrates can include glass, germanium, multilayered materials, group IV materials, and the like. The method includes moving the first alignment mark of the first substrate to the first silicon based pattern on the second substrate and moving the second alignment mark of the first substrate to the second silicon based pattern on the second substrate, as illustrated by
Preferably, the method maintains substantial parallel alignment between the first surface and the second surface during a portion of time associated with moving the first alignment mark to the first silicon based pattern and moving the second alignment mark with the second silicon based pattern. In a preferred embodiment, the method maintains the first alignment mark of the first substrate within about 40 microns or less of the first silicon based pattern on the second substrate and maintains the second alignment mark of the first substrate within about 40 microns or less of the second silicon based pattern on the second substrate. Preferably, the spacing can also be 20 microns and less or 10 microns and less, depending upon the embodiment.
As shown, the method illuminates 203 a portion of at least one of the first substrate or the second substrate with electromagnetic radiation source 201 (i.e., infrared) while the first surface is in substantial parallel alignment with the second substrate. The method also detects via detector 200 a signal 205 associated with a portion of the electromagnetic radiation and uses the signal associated with the detected portion of the electromagnetic radiation to align the first substrate with the second substrate using at least the first alignment mark and the first silicon based pattern or the second alignment mark and the second silicon based pattern. The method couples the first substrate with the second substrate by contacting the first surface with the second surface as shown in
It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
