# US 6,293,847 B1 · Apparatus for chemical mechanical polishing endpoint detection using a hydrogen sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,293,847 B1 - Document ID: US6293847B1 - Status: Granted - Kind: B1 - Application number: 09/418,087 - Filed: 1999-10-14 - Granted: 2001-09-25 - Earliest claimed: 1999-10-14 - Assignees: Agere Systems Guardian Corp. - Inventors: William Graham Easter; John Albert Maze; Frank Miceli; Sudhanshu Misra; Allen Yen - Web page: https://patentgrep.com/patent/US6293847B1 ## CPC - B24B 37/013: Devices or means for detecting lapping completion - B24B 49/10: involving electrical means (B24B49/02, B24B49/08 take precedence) - G01B 21/08: for measuring thickness - G01N 33/005: {H2} - B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract An apparatus for determining endpoint in the chemical mechanical polishing of a metal film using an acidic slurry includes a hydrogen sensor which senses the amount of hydrogen vapor being produced as a result of the reaction between the metal film and the acidic slurry. When the concentration of hydrogen vapor in the reaction area drops, endpoint is attained and the polishing operation may be terminated or otherwise adjusted. Hydrogen sensing elements include a palladium gate MOS transistor, expandable plastics and a tungsten oxide film. ## Claims ### Claim 1 In a chemical mechanical polishing apparatus which uses a polishing slurry, an endpoint detector comprising a hydrogen vapor sensor mounted in the chemical mechanical polishing apparatus in close proximity to an interface formed between a polishing pad and a surface being polished and adapted for sensing hydrogen vapor produced as a reaction product during a chemical mechanical polishing operation. ### Claim 2 (depends on 1) The endpoint detector as in claim 1, further comprising an electronic circuit coupled to the hydrogen vapor sensor. ### Claim 3 (depends on 1) The endpoint detector as in claim 1, in which the hydrogen vapor sensor includes a sensing element oriented such that the sensing element is exposed to a product stream being withdrawn from the chemical mechanical polishing operation. ### Claim 4 (depends on 1) The endpoint detector as in claim 1, wherein the hydrogen vapor sensor includes a sensing element having a characteristic which changes depending on an amount of hydrogen vapor present, and further comprising an electronic circuit capable of measuring the characteristic. ### Claim 5 (depends on 1) The endpoint detector as in claim 1, wherein the hydrogen vapor sensor includes a palladium gate MOS transistor as a sensing element. ### Claim 6 (depends on 5) The endpoint detector as in claim 5, further comprising an electronic circuit capable of reading a threshold voltage of the transistor. ### Claim 7 (depends on 1) The endpoint detector as in claim 1, wherein the hydrogen vapor sensor includes, as a sensing element plastic which expands when exposed to hydrogen vapor. ### Claim 8 (depends on 7) The endpoint detector as in claim 7, wherein the plastic includes a conductivity which changes when the plastic expands, and further comprising an electronic circuit capable of measuring the conductivity. ### Claim 9 (depends on 7) The endpoint detector as in claim 7, further comprising means for sensing an expansion of the plastic. ### Claim 10 (depends on 1) The endpoint detector as in claim 1, wherein the hydrogen vapor sensor includes a tungsten oxide film structure as a sensing element. ### Claim 11 (depends on 10) The endpoint detector as in claim 10, further comprising a palladium layer disposed over the tungsten oxide film structure. ### Claim 12 (depends on 10) The endpoint detector as in claim 10, wherein the tungsten oxide film includes a conductivity which changes when hydrogen is adsorbed onto the tungsten oxide film, and further comprising an electronic circuit capable of measuring the conductivity. ### Claim 13 (depends on 11) The endpoint detector as in claim 11, in which the palladium layer is substantially transparent. ### Claim 14 (depends on 10) The endpoint detector as in claim 10, wherein the tungsten oxide film comprises a hydrated oxide film represented by WO3.H2O. ### Claim 15 (depends on 10) The endpoint detector as in claim 10, wherein the tungsten oxide film changes coloration when hydrogen is adsorbed onto the film, and further comprising an optical instrument capable of measuring a refractive index of the film. ### Claim 16 In a chemical mechanical polishing apparatus which uses a polishing slurry, an endpoint detector comprising a hydrogen vapor sensor mounted in a chemical mechanical polishing apparatus in close proximity to a surface being polished, and adapted for sensing hydrogen vapor produced as a reaction product during a chemical mechanical polishing operation, and an electronic circuit coupled to the hydrogen vapor sensor. ### Claim 17 (depends on 16) The endpoint detector as in claim 16, wherein the hydrogen vapor sensor includes a sensing element having a characteristic which changes depending on an amount of hydrogen vapor present, and the electronic circuit is capable of measuring the characteristic. ### Claim 18 (depends on 17) The endpoint detector as in claim 17, wherein the sensing element comprises a tungsten oxide film and the characteristic comprises conductivity.