# US 8,785,938 B2 · Method for forming polycrystalline film, polycrystalline film and thin film transistor fabricated from the polycrystalline film > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,938 B2 - Document ID: US8785938B2 - Status: Granted - Kind: B2 - Application number: 13/583,851 - Filed: 2012-08-02 - Published: 2013-10-24 - Granted: 2014-07-22 - Earliest claimed: 2012-04-23 - Assignees: Tsinghua University - Applicants: Lianfeng Zhao; Renrong Liang; Mei Zhao; Jing Wang; Jun Xu - Inventors: Lianfeng Zhao; Renrong Liang; Mei Zhao; Jing Wang; Jun Xu - Web page: https://patentgrep.com/patent/US8785938B2 ## CPC - H10D 30/6731: {Top-gate only TFTs} - H10D 30/0314: {of lateral top-gate TFTs comprising only a single gate} - H10D 30/0321: {comprising silicon, e.g. amorphous silicon or polysilicon} - H10D 30/6745: {Polycrystalline or microcrystalline silicon} - H10D 62/40: Crystalline structures - H10D 86/0227: {using structural arrangements to control crystal growth, e.g. placement of grain filters} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A method for forming a polycrystalline film, a polycrystalline film formed by the method and a thin film transistor fabricated from the polycrystalline film are provided. The method comprises the steps of: providing a substrate; forming a thermal conductor layer on the substrate; etching the thermal conductor layer until the substrate is exposed to form a thermal conductor pattern; forming a seed layer on the thermal conductor layer and the substrate; etching the seed layer to form seed crystals on both sidewalls of the thermal conductor; forming an amorphous layer on the substrate, the thermal conductor layer and the seed crystals; etching the amorphous layer; and recrystallizing the amorphous layer to form a polycrystalline layer. ## Claims ### Claim 1 A method for forming a polycrystalline film, comprising steps of: providing a substrate; forming a thermal conductor layer on the substrate; etching the thermal conductor layer until the substrate is exposed to form a thermal conductor pattern; forming a seed layer on the thermal conductor layer and the substrate; etching the seed layer to form seed crystals on both sidewalls of the thermal conductor layer; forming an amorphous layer on the substrate, the thermal conductor layer and the seed crystals; etching the amorphous layer; and recrystallizing the amorphous layer to form a polycrystalline layer. ### Claim 2 (depends on 1) The method according to claim 1, further comprising: forming a passivation layer on the substrate, wherein the thermal conductor layer is formed on the passivation layer. ### Claim 3 (depends on 1) The method according to claim 1, wherein a material of the substrate is one of glass, plastics and silicon. ### Claim 4 (depends on 2) The method according to claim 2, wherein a material of the passivation layer is an oxide of silicon, silicon nitride, silicon carbide or a combination thereof. ### Claim 5 (depends on 1) The method according to claim 1, wherein a melting point of a thermal conductor of the thermal conductor layer is higher than a highest temperature of the thermal conductor layer during laser irradiation, the thermal conductor is a metal or a high temperature-resistant non-metallic material, and a thermal conductivity of the thermal conductor layer is higher than that of the polycrystalline layer. ### Claim 6 (depends on 1) The method according to claim 1, wherein the seed layer is a heterogeneous seed layer or a homogeneous seed layer, and a mismatch between a lattice constant of a material of the seed layer and N or 1/N times of the lattice constant of a material of the polycrystalline layer is not more than 30%, in which N is a positive integer. ### Claim 7 (depends on 6) The method according to claim 6, wherein a material of the heterogeneous seed layer is one of a metal silicide, a metal germanide, calcium fluoride, cerium oxide and zirconium oxide. ### Claim 8 (depends on 1) The method according to claim 1, wherein the recrystallizing step is performed by laser irradiation or rapid thermal processing. ### Claim 9 A polycrystalline film, comprising: a substrate; a thermal conductor layer formed on the substrate; seed crystals formed on both sidewalls of the thermal conductor layer; a polycrystalline layer formed on a part of the substrate which is not covered by the thermal conductor layer and the seed crystals. ### Claim 10 (depends on 9) The polycrystalline film according to claim 9, further comprising: a passivation layer formed on the substrate, wherein the thermal conductor layer is formed on the passivation layer, and the polycrystalline layer formed on a part of the passivation layer which is not covered by the thermal conductor layer and the seed crystals. ### Claim 11 (depends on 9) The polycrystalline film according to claim 9, wherein a material of the substrate is one of glass, plastics and silicon. ### Claim 12 (depends on 10) The polycrystalline film according to claim 10, wherein a material of the passivation layer is an oxide of silicon, silicon nitride, silicon carbide or a combination thereof. ### Claim 13 (depends on 9) The polycrystalline film according to claim 9, wherein a thermal conductor of the thermal conductor layer is a metal or a high temperature-resistant non-metallic material, and a thermal conductivity of the thermal conductor layer is higher than that of the polycrystalline layer. ### Claim 14 (depends on 9) The polycrystalline film according to claim 9, wherein the seed crystals are heterogeneous seed crystals or homogeneous seed crystals, and a mismatch between a lattice constant of a material of the seed crystals and N or 1/N times of the lattice constant of a material of the polycrystalline layer is not more than 30%, in which N is a positive integer. ### Claim 15 (depends on 14) The polycrystalline film according to claim 14, wherein a material of the heterogeneous seed crystals is one of a metal silicide, a metal germanide, calcium fluoride, cerium oxide and zirconium oxide. ### Claim 16 A thin film transistor, comprising: a substrate; a thermal conductor layer formed on the substrate; seed crystals formed on both sidewalls of the thermal conductor layer; a polycrystalline layer formed on a part of the substrate which is not covered by the thermal conductor layer and the seed crystals; a source and a drain formed in the polycrystalline layer respectively; a gate dielectric layer formed on the polycrystalline layer and a gate formed on the gate dielectric layer; and a source metal layer formed on the source and a drain metal layer formed on the drain. ### Claim 17 (depends on 16) The thin film transistor according to claim 16, further comprising: a passivation layer formed on the substrate, wherein the thermal conductor layer is formed on the passivation layer, and the polycrystalline layer formed on a part of the passivation layer which is not covered by the thermal conductor layer and the seed crystals. ### Claim 18 (depends on 16) The thin film transistor according to claim 16, wherein a thermal conductor of the thermal conductor layer is a metal or a high temperature-resistant non-metallic material, and a thermal conductivity of the thermal conductor layer is higher than that of the polycrystalline layer. ### Claim 19 (depends on 16) The thin film transistor according to claim 16, wherein the seed crystals are heterogeneous seed crystals or homogeneous seed crystals, and a mismatch between a lattice constant of a material of the seed crystals and N or 1/N times of the lattice constant of a material of the polycrystalline layer is not more than 30%, in which N is a positive integer.