The fabrication of a touch sensor panel having co-planar single-layer touch sensors fabricated on the back side of a cover glass is disclosed. It can be desirable from a manufacturing perspective to perform all thin-film processing steps on a motherglass before separating it into separate parts. To perform thin-film processing on a motherglass before separation, a removable sacrificial layer such as a photoresist can be applied over the thin-film layers.

Next, the motherglass can be scribed and separated, and grinding and polishing steps can be performed prior to removing the sacrificial layer. In alternative embodiments, after the protective sacrificial layer is applied, the bulk of the coverglass can be dry-etched using a very aggressive anisotropic etching that etches primarily in the z-direction. In this embodiment, the etching can be patterned using photolithography to create rounded corners or any other shape. The photoresist can then be removed.

Here's Apple's background and summary of the invention: Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize the touch and position of the touch on the display screen, and the computing system can interpret the touch and thereafter perform an action based on the touch event.

Touch sensor panels can be implemented as an array of pixels formed by multiple drive lines (e.g. rows) crossing over multiple sense lines (e.g. columns), where the drive and sense lines are separated by a dielectric material. An example of such a touch sensor panel is described in Applicant's co-pending U.S. application Ser. No. 11/650,049 entitled "Double-Sided Touch Sensitive Panel and Flex Circuit Bonding," filed on Jan. 3, 2007, the contents of which are incorporated by reference herein. However, touch sensor panels having drive and sense lines formed on the bottom and top sides of a single substrate can be expensive to manufacture. One reason for this additional expense is that thin-film processing steps must be performed on both sides of the glass substrate, which requires protective measures for the processed side while the other side is being processed. Another reason is the cost of the flex circuit fabrication and bonding needed to connect to both sides of the substrate.

This relates to the fabrication of a touch sensor panel having touch sensors fabricated on a substrate for detecting touch events (the touching of one or multiple fingers or other objects upon a touch-sensitive surface at distinct locations at about the same time). When forming a touch sensor panel on a substrate, if the substrate is singulated before processing, the separation step is relatively easy to accomplish with laser or wheel scribing and breaking, followed by optional grinding and polishing to achieve a cosmetically pleasing shape and touch. Because separation is performed before processing, protection of sensitive circuitry during grinding and polishing is not needed. However, it can be desirable from a manufacturing perspective to perform all processing steps on a substrate sheet before separating it into separate parts with rounded corners (in the case of no bezel).

To perform processing on a substrate sheet before separation, a removable sacrificial layer such as a photoresist can be applied over the sensitive circuitry. Next, the parts can be scribed and separated to get individual parts, and grinding and polishing steps can be performed prior to removing the sacrificial layer. In alternative embodiments, after the protective sacrificial layer is applied, the bulk of the substrate sheet can be dry-etched using a very aggressive anisotropic etching that etches primarily in the z-direction. This process is similar to reactive ion etching, in which photoresist is applied to the areas to be preserved, and the unwanted areas are then etched away. In this embodiment, the etching can be patterned using photolithography to create rounded corners or any other shape. The photoresist can then be removed.

In further alternative embodiments, dry etching can be utilized on a blank substrate sheet to etch partially through the sheet to form the radiused corners or other shapes. The substrate sheet can then be subjected to processing to apply various layers of the touch sensor panel, followed by laser scribing and breaking to singulate the parts. This process avoids the need to submit the sensitive layers to the bulk shaping etch process, which might damage them.

The inventors are Steve Porter Hotelling, John J. Zhong and Joseph Edward Clayton. The graphic below illustrates a partial top view of an exemplary substantially transparent touch sensor panel having co-planar single-layer touch sensors fabricated on a single side of a substrate according to one embodiment of this invention.