# US 9,437,670 B2 · Light activated test connections > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,437,670 B2 - Document ID: US9437670B2 - Status: Granted - Kind: B2 - Application number: 13/689,090 - Filed: 2012-11-29 - Published: 2014-05-29 - Granted: 2016-09-06 - Earliest claimed: 2012-11-29 - Assignees: Globalfoundries Inc. - Applicants: International Business Machines Corporation - Inventors: Nathaniel R. Chadwick; John B. DeForge; John J. Ellis-Monaghan; Jeffrey P. Gambino; Ezra D. Hall; Marc D. Knox; Kirk D. Peterson - Web page: https://patentgrep.com/patent/US9437670B2 ## CPC - H10D 99/00: Subject matter not provided for in other groups of this subclass - G01R 31/2856: {Internal circuit aspects, e.g. built-in test features; Test chips; Measuring material aspects, e.g. electro migration [EM]} - H10P 74/277: {Circuits for electrically characterising or monitoring manufacturing processes, e.g. circuits in tested chips or circuits in testing wafers} - G01R 31/2818: {using test structures on, or modifications of, the card under test, made for the purpose of testing, e.g. additional components or connectors (G01R31/2805 takes precedence; printed circuits having, e.g. symbols, test patterns or visualisation means H05K1/0266)} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 ## Abstract A test circuit including a light activated test connection in a semiconductor device is provided. The light activated test connection is electrically conductive during a test of the semiconductor device and is electrically non-conductive after the test. ## Claims ### Claim 1 A semiconductor structure, comprising: a test circuit comprising a light activated test connection in a semiconductor device, wherein the light activated test connection is electrically conductive during a test of the semiconductor device and is electrically non-conductive after the test, wherein the semiconductor device is a single chip of a three dimensional stacked chip system; and the light activated test connection is sacrificial. ### Claim 2 (depends on 1) The structure of claim 1, wherein the light activated test connection is converted from a non-conductive state to a conductive state by applying light. ### Claim 3 (depends on 1) The structure of claim 1, wherein the test circuit is connected between two through silicon vias in the semiconductor device. ### Claim 4 (depends on 3) The structure of claim 3, wherein the light activated test connection is structured and arranged as a switch between the two through silicon vias. ### Claim 5 (depends on 1) The structure of claim 1, wherein: the semiconductor device contains a silicon-based portion; the semiconductor device contains one or more silicon based devices; and the light activated test connection is composed of a material having a bandgap substantially less than that of silicon. ### Claim 6 (depends on 1) The structure of claim 1, wherein the semiconductor device comprises: an integrated circuit device formed in silicon; and at least one of an opaque structure and an isolation structure between the integrated circuit device and the light activated test connection. ### Claim 7 (depends on 1) The structure of claim 1, wherein the light activated test connection is arranged to be exposed to light during testing of the semiconductor device but the light activated test connection is covered when inserted into the three dimensional stacked chip system. ### Claim 8 (depends on 1) The structure of claim 1, wherein: the semiconductor device contains a silicon-based portion; the semiconductor device contains one or more silicon based devices; and the light activated test connection is composed of a material having a bandgap substantially greater than that of silicon. ### Claim 9 (depends on 8) The structure of claim 8, wherein: the bandgap of the material of the light activated test connection is about 1.6 eV; a light used for activating the light activated test connection is limited in area of exposure. ### Claim 10 (depends on 1) The structure of claim 1, wherein the light activated test connection is on and contacting a barrier layer in the semiconductor device. ### Claim 11 (depends on 1) The structure of claim 1, wherein the test circuit comprises the light activated test connection and a current source connected to a first input of a gate. ### Claim 12 (depends on 11) The structure of claim 11, wherein the test circuit comprises a test control signal connected to a second input of the gate. ### Claim 13 (depends on 12) The structure of claim 12, wherein an output of the gate provides a test control enable signal. ### Claim 14 A semiconductor structure, comprising: a test circuit comprising a light activated test connection in a semiconductor device, wherein the light activated test connection is electrically conductive during a test of the semiconductor device and is electrically non-conductive after the test, wherein the semiconductor device contains a silicon-based portion; the semiconductor device contains one or more silicon based devices; the light activated test connection is composed of Ge having a bandgap substantially less than that of silicon and that is between about 0.1 μm and about 1.0 μm thick in a vertical direction of the semiconductor device; and a light used for activating the light activated test connection has a wavelength of about 1350 nm. ### Claim 15 A semiconductor structure, comprising: a test circuit comprising a light activated test connection in a semiconductor device, wherein the light activated test connection is electrically conductive during a test of the semiconductor device and is electrically non-conductive after the test, wherein the light activated test connection is on and contacting a barrier layer in the semiconductor device; and wherein the semiconductor device comprises: the barrier layer; a first contact pad in a first opening in the barrier layer and contacting a first conductive path; and a second contact pad in a second opening in the barrier layer and contacting a second conductive path. ### Claim 16 (depends on 15) The structure of claim 15, wherein the light activated test connection comprises a layer of material contacting both the first contact pad and the second contact pad. ### Claim 17 A semiconductor structure, comprising: a test circuit comprising a light activated test connection in a semiconductor device, wherein the light activated test connection is electrically conductive during a test of the semiconductor device and is electrically non-conductive after the test; wherein the test circuit comprises the light activated test connection and a current source connected to a first input of a gate; and the current source is sized based on a leakage of the light activated test connection and a threshold of the gate.