TFT array inspection method and device
First Claim
1. A method of TFT array inspection comprising the steps of:
- charging a pixel capacitance CP constituting a pixel of a TFT array with a pixel voltage VP having a known value and charging an additional capacitance CT (CT>
>
CP) with a set voltage VS (VP≠
VS) having a known value, said additional capacitance CT including at least a line capacitance CS (CS>
>
CP) having an unknown value and said additional capacitance CT being connected in parallel with said pixel capacitance CP during inspection of said pixel, after the charging of both of these, connecting said pixel capacitance CP and said additional capacitance CT in parallel, and measuring a difference voltage Δ
VS between a voltage Va of said additional capacitance CT after the parallel connection and said set voltage VS, said charging and said connecting of said pixel capacitance CP and said additional capacitance CT and said measuring being conducted at least twice, by changing a value of said additional capacitance CT with use of at least one reference capacitance Δ
CS having a known value, thereby measuring at least two difference voltages Δ
VS having difference values; and
inspecting said pixel based on at least these two measured difference voltages Δ
VS and the following equation representing these difference voltages Δ
VS;
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Accused Products
Abstract
The pixel capacitances of an LCD array can be inspected easily and in a short time without being affected by the capacitance of the tester system. On the first occasion, pixel capacitance CP is charged with pixel voltage VP and line capacitance CS (CS>>CP) that is connected in parallel with pixel capacitance CP is charged with set voltage VS (VP≠VS). By connecting pixel capacitance CP and line capacitance CS is parallel, the difference voltage ΔVS1 of the voltage of the line capacitance CS after the parallel connection and the set voltage VS that is charged thereon before the parallel connection is measured. On the second occasion, pixel capacitance CP is charged with pixel voltage VP and a known reference capacitance ΔCS is connected in parallel with line capacitance CS, this being charged with set voltage VS. By further connecting in parallel pixel capacitance CP with the parallel-connected line capacitance and reference capacitance ΔCS, the difference voltage ΔVS2 of the line capacitance CS after this parallel connection and the set voltage VS that was charged thereon prior to the parallel connection is measured. The pixel capacitance CP is found from these difference voltages ΔVS1, ΔVS2 measured on the first and second occasion and an equation CP=ΔCS·ΔVS1·ΔVS2/((VP−VS)·(ΔVS1−ΔVS2)) derived from the difference voltages.
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Citations
15 Claims
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1. A method of TFT array inspection comprising the steps of:
-
charging a pixel capacitance CP constituting a pixel of a TFT array with a pixel voltage VP having a known value and charging an additional capacitance CT (CT>
>
CP) with a set voltage VS (VP≠
VS) having a known value, said additional capacitance CT including at least a line capacitance CS (CS>
>
CP) having an unknown value and said additional capacitance CT being connected in parallel with said pixel capacitance CP during inspection of said pixel, after the charging of both of these, connecting said pixel capacitance CP and said additional capacitance CT in parallel, and measuring a difference voltage Δ
VS between a voltage Va of said additional capacitance CT after the parallel connection and said set voltage VS, said charging and said connecting of said pixel capacitance CP and said additional capacitance CT and said measuring being conducted at least twice, by changing a value of said additional capacitance CT with use of at least one reference capacitance Δ
CS having a known value, thereby measuring at least two difference voltages Δ
VS having difference values; and
inspecting said pixel based on at least these two measured difference voltages Δ
VS and the following equation representing these difference voltages Δ
VS;
- View Dependent Claims (2, 3, 5, 11, 12)
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4. A TFT array inspection device comprising:
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a power source capable of selectively applying two voltages, namely, a pixel voltage VP and a set voltage VS (VP≠
VS);
a pixel of a TFT array including a pixel capacitance CP and a TFT switch SW1 connected in series to this pixel capacitance CP;
a line for connecting said power source to said pixel;
a line capacitance CS (CS>
>
CP) connected in parallel with said pixel capacitance CP on said pixel inspection;
a reference capacitance Δ
CS having a known value;
a switch SW2 for connecting in parallel or isolating said reference capacitance Δ
CS with respect to said line capacitance CS;
a switch SW3 for turning ON/OFF said line; and
a calculation control circuit whereby said pixel is inspected by controlling ON/OFF of said TFT switch SW1, switches SW2 and SW3, wherein said calculation control circuit performs ON/OFF of said TFT switches SW1, switches SW2 and SW3, such that first of all, said pixel capacitance CP is charged with said pixel voltage VP by connecting said power source to said line and said line capacitance CS is charged with said set voltage VS by isolating said pixel capacitance CP from said line, after charging up both of these, said power source and said pixel are isolated and said pixel capacitance CP and said line capacitance CS are connected in parallel whereby a difference voltage Δ
VS1 between a voltage Va1 of said line capacitance CS after the parallel connection and said set voltage Δ
VS is measured;
next, said reference capacitance Δ
CS and said line capacitance CS are connected in parallel, said power source is connected to said line thereby charging up said pixel capacitance CP with said pixel voltage CP, and, by isolating said pixel capacitance CP from said line, said reference capacitance Δ
CS and said line capacitance CS that were connected in parallel are charged with said set voltage VS and, after charging up both of these, said pixel voltage VP charged on to said pixel capacitance CP for a prescribed time is held, and said pixel capacitance CP after the lapse of a prescribed time is further connected in parallel with said parallel-connected reference capacitance Δ
CS and said line capacitance CS whereby a difference voltage Δ
VS2 between a voltage Va2 of said line capacitance CS after the parallel connection and said set voltage Δ
VS is measured,wherein a pixel parameter is inspected based on at least one difference voltage of said difference voltages Δ
VS1 and Δ
VS2, and a value of said pixel capacitance CP is obtained based on said difference voltages Δ
VS1 and Δ
VS2 and the following equation;
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6. A method of TFT array inspection comprising:
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a capacitance value setting process of setting at least two values as a value of an additional capacitance CT by changing the value of said additional capacitance CT with use of at least one reference capacitance Δ
CS having a known value, said additional capacitance CT including at least a line capacitance Cs having an unknown value and said additional capacitance CT being connected in parallel with a pixel capacitance CP constituting a pixel of a TFT array, during inspection of said pixel;
a charging process of charging said pixel capacitance CP with a pixel voltage VP having a known value and charging said additional capacitance CT with a set voltage VS having a known value different from said pixel voltage VP;
every time each of said at least two values of said additional capacitance CT is set by said capacitance value setting process;
a difference voltage measuring process of measuring at least two difference voltages Δ
VS having different values by measuring a difference voltage Δ
VS between said set voltage VS and a voltage Va of said additional capacitance CT after a parallel connection wherein said pixel capacitance CP and said additional capacitance CT are connected in parallel every time after said charging process is finished; and
a pixel inspecting process of inspecting said pixel based on said at least two difference voltages Δ
VS measured by said difference voltage measuring process.- View Dependent Claims (7, 8, 9, 10, 13, 14)
said capacitance value setting process is adapted to set two values as a value of said additional capacitance CT; - and
said difference voltage measuring process is adapted to measure two difference voltages Δ
VS as said at least two difference voltages Δ
VS.
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8. The method of TFT array inspection according to claim 6 wherein,
a value of said pixel voltage CP is set to be a smaller value than that of said set voltage VS; - and
said charging process is adapted to charge said pixel capacitance CP with said pixel voltage VP and to charge said additional capacitance CT with said set voltage VS by charging said additional capacitance CT with said set voltage VS after charging simultaneously said pixel capacitance CP and said additional capacitance CT with said pixel voltage VP.
- and
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9. The method of TFT array inspection according to claim 6 wherein,
said pixel inspecting process is adapted to obtain a value of said pixel capacitance CP based on said at least two difference voltages Δ - VS and a predetermined equation representing said at least two difference voltages Δ
VS.
- VS and a predetermined equation representing said at least two difference voltages Δ
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10. The method of TFT array inspection according to claim 9 wherein, said predetermined equation is the following equation:
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13. The method of TFT array inspection according to claim 8 wherein, said pixel parameter includes a plurality of pixel parameters including a leakage value of said pixel capacitance CP;
- and
said pixel inspecting process is adapted to divide said plurality of pixel parameters into said leakage value and pixel parameters other than said leakage value so as to inspect said leakage value and said pixel parameters other than said leakage value based on respective different voltages Δ
VS.
- and
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14. The method of TFT array inspection according to claim 6 wherein, said pixel inspecting process comprises:
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a pixel capacitance detecting process of detecting a value of said pixel capacitance CP based on said at least two difference voltages Δ
VS and a predetermined equation representing said at least two difference voltages Δ
VS and a predetermined equation representing said at least two difference voltages Δ
VS; and
a pixel parameter inspecting process of inspecting a pixel parameter to see whether said pixel parameter is good or not, based on at least one difference voltage Δ
VS of said at least two difference voltages Δ
VS.
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15. A TFT array inspection device comprising,
a capacitance value setting system which sets at least two values as a value of an additional capacitance CT by changing the value of said additional capacitance CT with use of at least one reference capacitance Δ - CS having a known value, said additional capacitance CT including at least a line capacitance CS having an unknown value and said additional capacitance CT being connected in parallel with a pixel capacitance CP constituting a pixel of a TFT array, during inspection of said pixel;
a charging system which charges said pixel capacitance CP with a pixel voltage VP having a known value and which charges said additional capacitance CT with a set voltage VS having a known value different from said pixel voltage VP, every time each of said at least two values of said additional capacitance CT is set by said capacitance value setting system;
a difference voltage measuring system which measures at least two difference voltages Δ
VS having different values by measuring a difference voltage Δ
VS between said set voltage VS and a voltage Va of said additional capacitance CT after a parallel connection wherein said pixel capacitance CP and said additional capacitance CT are connected in parallel every time after a charging process of said charging system is finished; and
a pixel inspecting system which inspects said pixel based on said at least two difference voltages Δ
VS measured by said difference voltage measuring system.
- CS having a known value, said additional capacitance CT including at least a line capacitance CS having an unknown value and said additional capacitance CT being connected in parallel with a pixel capacitance CP constituting a pixel of a TFT array, during inspection of said pixel;
Specification