NOVELTY - A silicon substrate (100) with support surface (110) and bottom surface (120) is provided. A noble metal structure (140) is formed on support surface to generate contact regions (150) and non-contact regions (160). Portion(s) of support surface and noble metal structure are exposed to etchant which is aqueous solution comprising oxidizing agent and acid. The contact regions are preferentially etched with etchant when compared to non-contact regions. The preferentially etching provides etch front (175). A through-silicon via is formed by metal-catalyzed wet etching process.    USE - Methods for forming through-silicon via feature used for forming wafer-level silicon interposer package (all claimed) for producing sub-receivers and receivers for concentrator photovoltaic modules.    ADVANTAGE - The method enables economical formation of through-silicon via feature having high aspect ratio and reduced porosity in side walls, with accurate control of etch characteristics. The wafer-level silicon interposer package containing through-silicon via feature has reduced thermal resistance and thermal expansion.    DETAILED DESCRIPTION - A silicon substrate having a support surface and a bottom surface separated from the support surface by a silicon substrate thickness is provided. A noble metal structure is formed on the support surface to generate contact regions which are in contact with or proximate to the noble metal structure, and non-contact regions which are not in contact with or are not proximate to the noble metal structure. Portion(s) of the support surface and noble metal structure are exposed to an etchant which is an aqueous solution comprising an oxidizing agent and an acid. The contact regions are preferentially etched with etchant when compared to non-contact regions. The preferentially etching provides etch front having etch front rate, and etch front direction which is normal to the silicon substrate support surface. The preferentially etching process is continuously carried out until etch front reaches the bottom surface. A through-silicon via is formed by metal-catalyzed wet etching process. INDEPENDENT CLAIMS are included for the following:    (1) method for forming recess feature in silicon substrate;    (2) method for forming wafer-level silicon interposer package; and    (3) wafer-level silicon interposer package.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining formation of through-silicon via.    Silicon substrate (100)    Support surface (110)    Bottom surface (120)    Noble metal structures (140)    Contact regions (150)    Non-contact regions (160)    Etch font (175)