Method for post-CMP conversion of a hydrophobic surface of a low-k dielectric layer to a hydrophilic surface

#The present invention relates to a method of making semiconductor devices, in particular, those that include low-k or ultra low-k dielectric layers, which have hydrophobic surfaces when initially deposited.

#Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers and between metal lines formed within each layer, capacitance increases. To address this problem, insulating materials that have a relatively low dielectric constant are being used in place of silicon dioxide to form the dielectric layer that separates the metal lines.

#Conventional single or dual damascene processes may be used to form metal lines within such low-k dielectric layers, e.g., to generate the structure 100 shown in FIG. 1b. FIG. 1a represents a cross-section of that structure prior to a polishing operation. In that figure, structure 100 includes substrate 101, upon which is formed low-k dielectric layer 102. After a trench has been etched into low-k dielectric layer 102, barrier layer 103 is deposited. In addition to lining the trench, barrier layer 103 extends across surface 104 of low-k dielectric layer 102. Conductive layer 105, which may comprise copper, fills the trench and covers barrier layer 103, where that layer rests on top of surface 104.

#FIGS. 1a-1b represent cross-sections of structures that may result after certain steps are used when making a semiconductor device.

#FIGS. 2a-2b illustrate a mechanism believed to cause a hydrophilic component to attach to a hydrophobic surface of a dielectric layer.

#FIGS. 3a-3b schematically represent apparatus that may be used, when carrying out an embodiment of the method of the present invention.

#A method is described for converting a hydrophobic surface of a dielectric layer to a hydrophilic surface. That method comprises forming on a substrate a dielectric layer that has a hydrophobic surface. A hydrophilic component is then coupled to the surface of that dielectric layer. In the following description, a number of details are set forth to provide a thorough understanding of the present invention. It will be apparent to those skilled in the art, however, that the invention may be practiced in many ways other than those expressly described here. The invention is thus not limited by the specific details disclosed below.

#In one embodiment of the method of the present invention, a hydrophilic component is coupled to a dielectric layer's hydrophobic surface by exposing the dielectric layer to a solution that comprises the hydrophilic component. Such a hydrophilic component may comprise a first moiety that is hydrophilic and a second moiety that may bind the hydrophilic component to the surface of the dielectric layer. When a hydroxyl group is located on the dielectric layer's surface, the second moiety may comprise a hydroxyl or alkoxy group. Such a moiety may react with the hydroxyl group located on the dielectric layer's surface to form a chemical bond between that surface and the hydrophilic component.

#Such a hydrophilic component may have the molecular formula (OX)yMAbZ, in which X is hydrogen or an alkyl group, y is between 1 and 3, M is a metal element, A comprises a constituent bonded to the metal element, b is between 0 and 2, and Z is a hydrophilic moiety. The hydrophilic moiety may comprise a polar moiety such as a carboxylic acid, aldehydic, phosphoric, sulfuric, or amino group. Particularly preferred are those that comprise a carboxylic acid or an amino group. Although a few examples of components—from which the hydrophilic moiety may be made—are given here, those skilled in the art will appreciate that others may be used instead. Similarly, the hydrophilic moiety may consist solely of one of these listed components, or, alternatively, may comprise a combination of those components, and/or others. The metal may comprise silicon, aluminum, or any other metal that may bind to the component's hydrophilic group and its hydroxyl or alkoxy group or groups.