Abstract: A thin film solar cell and process for forming the same. The solar cell includes a bottom electrode layer, a light absorbing semiconductor layer, and top electrode layer. The absorber layer includes a p-type interior region and an n-type exterior region formed around the perimeter of the layer from a modified native portion of the p-type interior region, thereby forming an active n-p junction that is an intrinsic part of the absorber layer. The top electrode layer is electrically connected to the bottom electrode layer via a scribe line formed in the absorber layer that defines sidewalls. The n-type exterior region of the absorber layer extends along both the horizontal top of the absorber layer, and onto the vertical sidewalls of the scribe line to increase the area of available n-p junction in the solar cell thereby improving solar conversion efficiency.

Abstract: The application provides an optoelectronic device structure, comprising a semiconductor stack, comprising a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; a first electrode electrically connecting with the first conductivity type semiconductor layer, and further comprising a first extension electrode; a second electrode electrically connecting with the second conductivity type semiconductor layer; and a plurality of electrical restraint contact areas between the semiconductor stack and the first extension electrode, wherein the plurality of electrical restraint contact areas is distributed in a variable interval.

Abstract: A photoelectric conversion device comprising a photoelectric conversion part including a first electrode layer, a second electrode layer and a photoelectric conversion layer provided between the first electrode layer and the second electrode layer, wherein light is made incident from an upper part of the second electrode layer into the photoelectric conversion layer; the photoelectric conversion layer generates a charge containing an electron and a hole corresponding to the incident light from the upper part of the second electrode layer; and the first electrode layer works as an electrode for extracting the hole.

Abstract: A method for forming a thin film photovoltaic device having patterned electrode films includes providing a soda lime glass substrate with an overlying lower electrode layer comprising a molybdenum material. The method further includes subjecting the lower electrode layer with one or more pulses of electromagnetic radiation from a laser source to ablate one or more patterns associated with one or more berm structures from the lower electrode layer. Furthermore, the method includes processing the lower electrode layer comprising the one or more patterns using a mechanical brush device to remove the one or more berm structures followed by treating the lower electrode layer comprising the one or more patterns free from the one or more berm structures. The method further includes forming a layer of photovoltaic material overlying the lower electrode layer and forming a first zinc oxide layer overlying the layer of photovoltaic material.

Abstract: An integrated back sheet for a back-contact solar cell module and a back-contact solar cell module made with such an integrated back-sheet are provided. Processes for making such integrated back-sheets and back-contact solar cell modules are also provided. Elongated electrically conductive wires that extend at least two times the length of solar cells in the back-contact cell module are mounted on a layer of the integrated back-sheet. The elongated conductive wires of the integrated back-sheet electrically connect to solar cell back contacts when the back-sheet is used in a back-contact photovoltaic module.

Abstract: A back-contact solar cell module includes an array of back-contact solar cells electrically connected in series by elongated electrically conductive wires incorporated into the solar module behind the solar cells. A process form making such back-contact solar modules is also provided.

Abstract: Embodiments of the invention contemplate the formation of a high efficiency solar cell using a laser patterning process to form openings in a passivation layer on a surface of a solar cell substrate. In one embodiment, a method of forming an opening in a passivation layer on a solar cell substrate includes forming a passivation layer on a back surface of a substrate, the substrate having a first type of doping atom on the back surface of the substrate and a second type of doping atom on a front surface of the substrate, and providing a series of laser pulses to the passivation layer for between about 500 picoseconds and about 80 nanoseconds to form openings in the passivation layer.

Abstract: Methods for increasing the power output of a TFPV solar panel using thin absorber layers comprise techniques for roughening and/or texturing the back contact layer. The techniques comprise roughening the substrate prior to the back contact deposition, embedding particles in sol-gel films formed on the substrate, and forming multicomponent, polycrystalline films that result in a roughened surface after a wet etch step, etc.

Abstract: A process for making a back-contact solar cell module is provided. Electrically conductive wires of an integrated back-sheet are physically and electrically attached to the back contacts of the solar cells of a solar cell array through openings in a polymeric interlayer dielectric layer using an electrically conductive binder before thermal lamination of the module.

Abstract: Embodiments of the present invention generally provide improved processes and apparatus for removing passivation layers from a surface of photovoltaic cells and improving contact resistance in rear point contact photovoltaic cells. In one embodiment, a method of processing a solar cell substrate includes providing a substrate having a passivation layer deposited on a first surface of the substrate. The passivation layer is a layer stack comprising an aluminum oxide and a silicon nitride. The method also includes exposing the first surface of the substrate to an etchant, and heating the etchant to dissolve the aluminum oxide of the passivation layer on the first surface. The method may further include forming a metal containing layer on a second surface of the substrate that is opposite to the first surface.

Abstract: A flexible solar battery module includes a flexible insulating base and a plurality of solar batteries separately disposed on the flexible insulating base. The solar battery includes a substrate disposed on the flexible insulating base, a first electrode disposed on the substrate, a photoelectric transducing layer disposed on the first electrode and exposing parts of the first electrode, and a second electrode disposed on the photoelectric transducing layer. The flexible solar battery module further includes an insulating layer disposed on the exposed first electrode of each solar battery and the exposed flexible insulating base between the adjacent solar batteries, and an auxiliary electrode disposed on the second electrode of each solar battery and the exposed first electrode of the adjacent solar battery for setting the plurality of solar batteries in a series connection.

Abstract: A thin film solar cell module according to an embodiment of the invention includes a substrate, a plurality of solar cells each including a first electrode on the substrate, a second electrode on the first electrode, and a photoelectric conversion unit between the first electrode and the second electrode, a ribbon positioned on each of first and second outermost solar cells among the solar cells, and a conductive adhesive part positioned between the first outermost solar cell and the ribbon and between the second outermost solar cell and the ribbon. The conductive adhesive part positioned between the second electrode of the first outermost solar cell and the ribbon includes a first connector, which is electrically connected to the first electrode, the photoelectric conversion unit, and the second electrode of the first outermost solar cell.

Abstract: A back side illumination image sensor reduced in chip size has a capacitor disposed in a vertical upper portion of a pixel region in the back side illumination image sensor in which light is illuminated from a back side of a subscriber, thereby reducing a chip size, and a method for manufacturing the back side illumination image sensor. The capacitor of the back side illumination image sensor reduced in chip size is formed in the vertical upper portion of the pixel region, not in the outside of a pixel region, so that the outside area of the pixel region for forming the capacitor is not required, thereby reducing a chip size.

Abstract: A wafer level packaged integrated circuit includes an array of contacts, a silicon layer and a glass layer. The silicon and glass layers are bonded together to form a bonding material layer therebetween. The bonding material layer includes gaps between the silicon layer and the glass layer at areas where no bonding material is present. An array of contacts is adjacent the semiconductor layer on a side thereof opposite the bonding layer. The wafer level packaged integrated circuit is provided with additional bonding material layer portions within the gaps and aligned with at least some of the contacts. When the wafer level packaged integrated circuit is configured as an image sensor or display having a pixel array, the additional bonding material layer portions are not used in an area of the pixel array.

Abstract: Manufacturing a semiconductor device includes preparing a structure including a semiconductor substrate having a first region and a second region, a first insulating film arranged on the first region, a second insulating film arranged on the first insulating film, a third insulating film arranged on the second insulating film, a fourth insulating film arranged on the second region, a fifth insulating film arranged on the fourth insulating film, and a sixth insulating film arranged on the fifth insulating film, etching the second insulating film and the first insulating film under different etching conditions after etching the third insulating film, and continuously etching the fifth insulating film and the fourth insulating film under the same etching conditions after etching the sixth insulating film.

Abstract: A photovoltaic device, and a method of fabricating the same are provided. Here, a base portion and an emitter portion are formed on a surface of a semiconductor substrate. An insulation layer is formed on the base portion and the emitter portion. The insulation layer has a plurality of vias to partially expose the base portion and the emitter portion. A first electrode is formed to contact a region of the emitter portion through at least one of the vias, and a second electrode is formed to contact a region of the base portion through at least another one of the vias. Then, a dicing line is set at a bus electrode portion of the second electrode, and the semiconductor substrate is split into at least two photovoltaic devices at the base portion along the dicing line.

Abstract: Systems and methods for cavity mode enhancement in dye-sensitized solar cells are provided. A dye-sensitized solar cell generally comprises a transparent substrate, an anode layer, an oxide layer, a dye layer, a cathode, and an electrolyte. The anode layer is deposited on a surface of the transparent substrate. The oxide layer is deposited on the anode layer and the dye is deposited on the oxide layer. A cathode is disposed adjacent to the dye layer and an electrolyte is disposed between the anode layer and the cathode.

Abstract: A solid-state imaging device includes a first substrate including a light-sensing portion configured to perform photoelectric conversion of incident light and a wiring portion provided on a light-incident side; an optically transparent second substrate provided on a wiring portion side of the first substrate at a certain distance; a through-hole provided in the first substrate; a through-via provided in the through-hole; a front-surface-side electrode connected to the through-via and provided on a front surface of the first substrate; a back-surface-side electrode connected to the through-via and provided on a back surface of the first substrate; and a stopper electrode provided on the front-surface-side electrode and filling a space between the front-surface-side electrode and the second substrate.

Abstract: A method for manufacturing thin film solar cells, includes forming a light permeable first electrode layer in the back light surface of a glass substrate, and formed in the first electrode layer a plurality of first openings for exposing a part of the back light surface therefrom; forming a photoelectric conversion layer on the first electrode layer and the exposed back light surface, and forming a plurality of second openings in the photoelectric conversion layer for exposing a part of the first electrode layer therefrom; and forming a glistening second electrode layer having a plurality of third openings formed therein, wherein the second electrode layer comprises a conductive colloid comprised of non-diffractive fillings and polymeric base material.

Abstract: A solar battery module includes a substrate, a plurality of first striped electrodes separately formed on the substrate, a plurality of striped photoelectric transducing layers respectively formed on the corresponding first striped electrode and the substrate wherein parts of the first striped electrode are exposed, a plurality of second striped electrodes respectively formed on the corresponding striped photoelectric transducing layer, and a plurality of conductive layers respectively formed on a side of the corresponding second striped electrode and the first striped electrode adjacent to the side, and not contacting the other second striped electrode.

Abstract: A black silicon solar cell includes a metal back electrode, the crystal silicon, a black silicon layer, a passivation layer and a metal gate; wherein, the metal back electrode is located on the back surface of the crystal silicon, the black silicon layer is located on the crystal silicon, the passivation layer is located on the black silicon layer, the metal gate is located on the passivation layer. The fabrication method includes: carrying out pretreatment of the silicon wafer; preparing the black silicon layer on the surface of the pretreated silicon wafer by using plasma immersion ion implantation technology; preparing an emitter on the black silicon layer, and carrying out passivation treatment on the emitter to form the passivation layer; respectively preparing the metal back electrode and the metal gate on the back surface of the single crystal silicon wafer and the passivation layer, respectively.

Abstract: Disclosed is a method for making a nickel film for use as an electrode of an n-p diode or solar cell. A light source is used to irradiate an n-type surface of the n-p diode or solar cell, thus producing electron-hole pairs in the n-p diode or solar cell. For the electric field effect at an n-p interface, electrons drift to and therefore accumulate on the n-type surface. With a plating agent, the diode voltage is added to the chemical potential for electroless plating of nickel on the n-type surface. The nickel film can be used as a buffer layer between a contact electrode and the diode or solar cell. The nickel film reduces the contact resistance to prevent a reduced efficiency of the diode or solar cell that would otherwise be caused by diffusion of the atoms of the electrode in following electroplating.

Abstract: The composition for forming a composition for forming a p-type diffusion layer, the composition containing a glass powder and a dispersion medium, in which the glass powder includes an acceptor element and a total amount of a life time killer element in the glass powder is 1000 ppm or less. A p-type diffusion layer and a photovoltaic cell having a p-type diffusion layer are prepared by applying the composition for forming a p-type diffusion layer, followed by a thermal diffusion treatment.

Abstract: Disclosed is a non-planar energy transducer, including a substrate and a switching device disposed thereon. An elastomer having a periodic structure is disposed on the switching device. A bottom electrode is conformally disposed on the elastomer to electrically connect to the switching device. An energy conversion layer is conformally disposed on the bottom electrode, and a top electrode is conformally disposed on the energy conversion layer, wherein the top electrode connects to a positive voltage or a negative voltage.

Abstract: The present invention relates to a cathode for use in a dye-sensitised solar cell which comprises a redox couple, wherein the cathode comprises: (a) metallic nickel; and (b) intrinsically conducting polymer that, during operation of the cell, reduces an oxidised species of the redox couple.

Abstract: A method and apparatus provide for a roughened back surface of a semiconductor absorber layer of a photovoltaic device to improve adhesion. The roughened back surface may be achieved through an etching process.

Abstract: In a method for producing a solar cell, a layer stack of dielectric layers is applied to a back of a solar cell substrate and the layer stack is heated and is held at temperatures of at least 700° C. during a time period of at least 5 minutes. The novel solar cell has a layer stack of dielectric layers on its back. At least one of the dielectric layers of the layer stack is densified so that its resistivity to firing-through of pastes with glass components is enhanced.

Abstract: A process for the formation of an electrically conductive silver back electrode of a PERC silicon solar cell comprising the steps: (1) providing a p-type silicon wafer having on its front-side an n-type emitter with an ARC layer thereon and on its back-side a perforated dielectric passivation layer with local BSF contacts at the places of the perforations, (2) applying and drying a silver paste to form a silver back electrode pattern connecting the local BSF contacts on the back-side of the silicon wafer, and (3) firing the dried silver paste, whereby the wafer reaches a peak temperature of 700 to 900° C., wherein the silver paste has no or only poor fire-through capability and comprises particulate silver and an organic vehicle.

Abstract: In a package process of backside illumination image sensor, a wafer including a plurality of pads is provided. A first carrier is processed to form a plurality of blind vias therein. The first carrier is adhered to the wafer so that the blind vias face to the pads correspondingly. A spacing layer is formed and a plurality of sensing components are disposed. A second carrier is adhered on the spacing layer. Subsequently, a carrier thinning process is performed so that the blind vias become the through holes. An insulating layer is formed on the first carrier. An electrically conductive layer is formed on the insulating layer and filled in the though holes to electrically connect to the pads. The package process can achieve the exact alignment of the through holes and the pads, thereby increasing the package efficiency and improving the package quality.

Abstract: A photodetector includes a substrate and an insulating arrangement formed in the substrate. The insulating arrangement electrically insulates a confined region of the substrate. The confined region is configured to generate free charge carriers in response to an irradiation. The photodetector further includes a read-out electrode arrangement configured to provide a photocurrent formed by at least a portion of the free charge carriers that are generated in response to the irradiation. The photodetector also includes a biasing electrode arrangement that is electrically insulated against the confined region by means of the insulating arrangement. The biasing electrode arrangement is configured to cause an influence on a spatial charge carrier distribution within the confined region so that fewer of the free charge carriers recombine at boundaries of the confined region compared to an unbiased state.

Abstract: A method to fabricate monolithically-integrated optoelectronic module apparatuses (100) comprising at least two series-interconnected optoelectronic components (104, 106, 108). The method includes deposition and scribing on an insulating substrate or superstate (110) of a 3-layer stack in order (a, b, c) or (c, b, a) comprising: (a) back-contact electrodes (122, 124, 126, 128), (b) semiconductive layer (130), and (c) front-contact components (152, 154, 156, 158). Via holes (153, 155, 157) are drilled so that heat of the drilling process causes a metallization at the surface of said via holes that renders conductive the semi-conductive layer's surface (132, 134, 136, 138) of said via holes, thereby establishing series-interconnecting electrical paths between optoelectronic components (104, 106, 108) by connecting first front-contact components (154, 156) to second back-contact electrodes (124, 126).

Abstract: Disclosed is an apparatus and method for generating inverted organic solar cells and which required no electron selective layer, were fabricated and their power conversion efficiency was found to improve irreversibly with post-processing light soaking for a period. X-Ray photoelectron spectroscopy characterization further revealed segregation in surface composition at the interface and was found to explain the current density-voltage measurements. In addition, the light soaked devices were found to exhibit an extended lifetime as compared to conventional devices. Since no electron selective layer was required, light soaking may be considered as a cost-effective method to achieve efficient inverted organic solar cells.

Abstract: The invention is directed to a polymer thick film silver composition comprising: (a) conductive silver flake (b) organic medium comprising (1) phenoxy organic polymeric binder and (2) organic solvent. The composition may be processed at a time and energy sufficient to remove all solvent. The invention is further directed to method(s) of grid formation on top of Thin-Film photovoltaic cells.

Abstract: The present invention relates to a method for manufacturing a flexible photoelectrode and a dye-sensitized solar cell using the same. More specifically, the method for manufacturingg a photoelectrode comprises forming a nanoparticle metal oxide layer on a flexible substrate, adsorbing dyes, and then, coating polymer, thereby forming a nanoparticle metal oxide layer consisting of nanoparticle metal oxide-dye-polymer. According to the present invention, the polymer penetrated between the nanoparticle metal oxide after dye adsorption may increase adhesion to the substrate and improve mechanical properties. Particularly, when applied for a flexible substrate such as a plastic substrate, bending property is excellent, and it may be useful for a flexible dye-sensitized solar cell having durability.

Abstract: The present invention relates to a contacted solar cell which has contact places on the front- and rear-side for electrical contacting of the solar cell. The current produced by the solar cells is tapped across the solar cells by means of a conductor fitted on the front- or rear-side, the contact places of the solar cell being arranged, according to the invention, on the front- or rear-side such that, in projection on the front-face of the solar cell, they do not come to coincide.

Abstract: A device, system, and method for a multi-junction solar cell is described herein. An exemplary silicon germanium solar cell structure has a substrate with a graded buffer layer grown on the substrate. A base layer and emitter layer for a first solar cell are grown in or on the graded buffer layer. A first junction is provided between the emitter layer and the base layer. A second solar cell is grown on top of the first solar cell.

Abstract: A process for the production of a LFC-PERC silicon solar cell having an aluminum back electrode wherein an aluminum paste having no or only poor fire-through capability and including particulate aluminum, glass frit, an organic vehicle and 0.01 to <0.05 wt. % of at least one antimony oxide, based on total aluminum paste composition, is used, and wherein the at least one antimony oxide is present in the aluminum paste as separate particulate constituent(s) and/or as glass frit constituent(s).

Abstract: An image pickup device includes a plurality of first electrodes, a second electrode, a third electrode, a photoelectric conversion layer, a plurality of signal reading portions, at least one of electric potential adjusting portions. The plurality of first electrodes is arranged on an upper side of a substrate in two dimensions with a predetermined gap interposed between one of the first electrodes and another first electrode adjacent to the one of the first electrode. The second electrode is arranged next to the first electrodes arranged on an outermost side of the first electrodes with the predetermined gap interposed between the first electrodes arranged on the outermost side and the second electrode. The third electrode faces both of the plurality of first electrodes and the second electrode. The photoelectric conversion layer is disposed between the plurality of first electrodes and the second electrode and the third electrode.

Abstract: A conductive paste composition contains a source of an electrically conductive metal, a lead-tellurium-based oxide, and an organic vehicle. An article such as a high-efficiency photovoltaic cell is formed by a process of deposition of the lead-free paste composition on a semiconductor substrate (e.g., by screen printing) and firing the paste to remove the organic vehicle and sinter the metal and lead-tellurium-based oxide.

Abstract: Disclosed is a method for surface-treating a semiconductor substrate to thereby reduce loss of minority carriers caused by surface recombination and improve the lifetime. In the method, a semiconductor substrate is prepared. An acid additive and an alkaline additive are added to water to obtain an aqueous solution having a pH of not more than 7. The aqueous solution comprises no hydrofluoric acid. A dangling bond at a surface of the semiconductor substrate is hydrogen-terminated. The surface, at which the dangling bond has been hydrogen-terminated, is brought into contact with the aqueous solution.

Abstract: A method of manufacturing a dye sensitised solar cell or other mesoscopic solar cell, including the steps of coating at least a portion of a surface of a substrate with an electrode film or other functional layer, and applying an isostatic pressure over the coated substrate to thereby compact the electrode film or functional layer on the substrate.

Abstract: A detector element is disclosed with a semi-conductive converter element and metal contacts arranged thereon for at least one anode and at least one cathode, wherein at least one of the metal contacts comprises a contact layer made from a contact material based on precious metal and ruthenium as its mixed component. Moreover, an embodiment of the invention concerns a radiation detector with the detector element with a ruthenium-containing contact layer and, optionally, with an evaluation unit to read out a detector signal, as well as a medical device with the radiation detector. Furthermore, a method for the production of a detector element is described which includes the installation step of a contact material of at least one of the metal contacts on the converter element, wherein the contact material includes a precious metal base with ruthenium as its mixed component.

Abstract: Included are a semiconductor substrate including, on one surface side, a dopant diffusion layer, a light-receiving surface side electrode electrically connected to the dopant diffusion layer and formed on the one surface side of the semiconductor substrate, and a rear surface side electrode formed on the other surface side of the semiconductor substrate. A first unevenness structure including first projected sections each having a square pyramid shape in a light-receiving surface side electrode formation region in which the light-receiving surface side electrode is formed on the one surface side of the semiconductor substrate including the dopant diffusion layer. A second unevenness structure including second projected sections each having a square pyramid shape larger than the first projected sections in a region where the light-receiving surface side electrode is not formed on the one surface side of the semiconductor substrate including the dopant diffusion layer.

Abstract: Certain embodiments provide a solid-state imaging apparatus including a first impurity layer, a second impurity layer, a third impurity layer, and an electrode. The first impurity layer is a photoelectric conversion layer, and is formed to have a constant depth on a semiconductor substrate. The second impurity layer is formed on a surface of the first impurity layer, to have a depth which becomes shallower toward a direction from the first impurity layer to the third impurity layer. The third impurity layer is formed in a position spaced apart from the first impurity layer and the second impurity layer on the surface of the semiconductor substrate. The electrode can transport electric charges from the first impurity layer to the third impurity layer, and is formed between the second impurity layer and the third impurity layer, on the surface of the semiconductor substrate.

Abstract: The present invention is directed to an electrically conductive composition comprising (a) an electrically conductive metal; (b) a Rh-containing component; (c) a Pb—Te—O; and (d) an organic medium; wherein the electrically conductive metal, the Rh-containing compound, and the Pb—Te—O are dispersed in the organic medium. The present invention is further directed to an electrode formed from the composition and a semiconductor device and, in particular, a solar cell comprising such an electrode. Also provided is a process for forming such an electrode. The electrodes provide good adhesion and good electrical performance.

Abstract: It is an object to provide a photoelectric conversion device with high photoelectric conversion efficiency that improves reliability by increasing contact force between a light absorbing layer and an electrode layer. The photoelectric conversion device includes an electrode layer, and a light absorbing layer located on the electrode layer. The light absorbing layer contains a compound semiconductor. The light absorbing layer comprises a first layer close to the electrode layer and a second layer located on the first layer. The first layer has a void ratio lower than that of the second layer.

Abstract: A method for calculating an offset value for aligned deposition of a second pattern onto a first pattern, comprising steps of: (a) loading a substrate with the first pattern on a surface of the substrate into a pattern recognition device at an original position inside the pattern recognition device; (b) determining a coordinate of a prescribed point of the first pattern by the pattern recognition device; (c) superimposing the second pattern onto the first pattern on the surface of the substrate; (d) bringing back the substrate with the first pattern and the second pattern into the original position inside the pattern recognition device; (e) determining a coordinate of a prescribed point of the second pattern by the pattern recognition device; wherein the prescribed point of the first pattern corresponds to the prescribed point of the second pattern; and (f) calculating the offset value between the first pattern and the second pattern.

Abstract: Disclosed are a solar cell apparatus and a method of fabricating the same. The A solar cell apparatus includes a substrate; a back electrode layer on the substrate; a light absorbing layer on the back electrode layer; and a window layer on the light absorbing layer, wherein the light absorbing layer is formed with a third through hole having a first width, and the window layer is formed with a fourth through hole having a second width larger than the first width, and the fourth through hole corresponds to the third through hole.

Abstract: A pixel array substrate including a substrate and a plurality of pixel structures is provided. Each pixel structure includes a patterned metal layer, an insulating layer, a patterned semiconductor layer and a data line layer. The patterned metal layer includes a gate line and a common electrode line. The patterned semiconductor layer includes a channel layer and a photosensitive resistance layer. The channel layer is disposed above and overlaps a part of the gate line. The data line layer includes a patterned first data line, a second data line and a third data line. The first and the second data lines are coupled to the channel layer and combine with the channel layer and the gate line to compose an active component. The second and the third data lines are coupled to the photosensitive resistance layer and combine with the photosensitive resistance layer to compose a light detecting component.

Abstract: An integrated circuit structure includes an interconnect structure that includes a plurality of metal layers, wherein the interconnect structure is under a semiconductor substrate. A metal pad is formed in one of the plurality of metal layers. A dielectric pad extends from a bottom surface of the semiconductor substrate up into the semiconductor substrate. An opening extends from a top surface of the semiconductor substrate down to penetrate through the semiconductor substrate and the dielectric pad. An edge of the semiconductor substrate in the opening is vertically aligned to an edge of the dielectric pad in the opening. The opening stops on a top surface of the metal pad. A dielectric spacer is disposed in the opening, wherein the dielectric spacer is formed on the edge of the semiconductor substrate and the edge of the dielectric pad.