Patent Application
20050052500
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1. Field of the Invention
The present invention relates to printers. More particularly, the present invention relates to ink jet printers.
2. General Background of the Invention
Inkjet print heads require well-controlled substrate temperature to maintain a consistent ink viscosity and jetting performance. Previous designs include a temperature sense resistor (TSR) integrated into the heater chip to monitor the substrate temperature. The chip also has designated resistor elements to heat the substrate as necessary. The resistor elements may have dedicated power FETs to control the substrate heater resistors, as in Lexmark's U.S. Pat. No. 6,102,515 (incorporated herein by reference). Some designs may use the inkjet resistors themselves for substrate heating, if the on-time is less than the bubble nucleation threshold, as practiced by Hewlett-Packard. The printer control unit periodically monitors the temperature sense resistor to determine the substrate temperature. Then the control unit turns the substrate heaters on and off, accordingly, to maintain the proper substrate temperature for optimum jetting performance.
The temperature sense resistor value follows the equations:
RT=Rambient*(1+(a*(T−Tambient)))
Rambient=RS ambient*(L/W)
The following U.S. patents, and all patents mentioned herein, are incorporated herein by reference:
U.S. Pat. No. 6,336,713 discloses a thermal inkjet printhead which uses metal silicon nitride resistors as heaters. This patent mentions that resistors having high bulk resistivity are desirable for use in thermal inkjet printing units, and that the resistors disclosed therein have high bulk resistivity (see column 8, lines 29).
U.S. Pat. No. 6,443,558 discloses an inkjet printhead having a thermal bend actuator with a separate titanium nitride heater element. It includes N-well transistors (see column 15).
U.S. Pat. No. 6,171,880 discloses a meandering polysilicon heater mounted on an IC CMOS chip. See column 4, lines 12-18 and 34-41, and column 5, lines 7-36 (fabricated in a CMOS N-well operation).
U.S. Pat. No. 6,382,758 discloses an inkjet printhead having TSRs 14 (see column 3, lines 1-5).
U.S. Pat. No. 6,450,622 discloses a print head with a semiconductor substrate that has an N-well layer, but uses TaAl resistors (see column 3, lines 6-7 and 44-46).
U.S. Pat. No. 5,136,305 discloses controlling heat to ink reservoirs for inkjet printheads using temperature sensitive resistors (see column 4, lines 30-38).
U.S. Pat. No. 5,300,968 discloses a lightly n-doped resistor or a heavily n+doped polysilicon resistor (both of which have high sheet resistance and high temperature coefficient of resistance) in a temperature compensating circuit in an inkjet printhead (see column 5, line 65 through column 6, line 30).
U.S. Pat. No. 6,441,680 discloses a CMOS reference voltage generator using p-type and n-type CMOS transistors. It discusses temperature dependence of these transistors (see, for example, column 4, lines 8-20).
The present invention focuses on the temperature sensitive resistor (TSR) in inkjet print heads. More specifically, the present invention comprises TSRs made of implants (such as of N-well material) in inkjet print heads, inkjet print heads including these TSRs, and inkjet printers including these inkjet print heads.
The present invention includes an inkjet print head chip having MOS logic blocks, resistor elements to heat the chip, and a controller of the resistor elements, and temperature sense resistors implanted in the chip, the temperature sense resistors being operatively connected to the controller of the resistor elements to enable the controller to monitor the chip temperature to control the resistor elements to heat the chip.
The present invention also includes a method of controlling the temperature of an inkjet print head chip having MOS logic blocks, comprising providing the print head chip with at least one substrate heater to heat the chip, providing the print head chip with a controller of the substrate heater, implanting temperature sense resistors in the chip, operatively connecting the temperature sense resistors to the controller of the substrate heater to enable the controller to monitor the chip temperature to control the substrate heater to heat the chip, and using the controller to control the substrate heater to heat the chip.
The temperature sense resistors preferably have a sheet resistance of at least 20 Ω/and a temperature coefficient of resistivity of at least 0.0010 Ω/° C. More preferably, the temperature sense resistors have a sheet resistance of at least 75 Ω/and a temperature coefficient of resistivity of at least 0.0020 Ω/° C. Even more preferably, the temperature sense resistors have a sheet resistance of at least 500 Ω/and a temperature coefficient of resistivity of at least 0.0030 Ω/° C. Most preferably, the temperature sense resistors have a sheet resistance of at least 1000 Ω/and a temperature coefficient of resistivity of at least 0.0040 Ω/° C.
The temperature sense resistors preferably comprise N-Well material, but could also comprise NSD material, LDD material, or PSD material, for example. An inkj et print head chip can include, for example, 1-1000 temperature sense resistors of the present invention.
Typically, each temperature sense resistor can be 0.05-5000 μm wide by 0.01-400,000 μm long by 0.05-4 μm thick. Preferably, each temperature sense resistor is 1-2000 μm wide by 1-200,000 μm long by 0.1-3 μm thick. More preferably, each temperature sense resistor is 2-1000 μm wide by 2-100,000 μm long by 0.2-2 μm thick.
In the present invention, the MOS logic blocks are preferably CMOS logic blocks.
The novel TSRs of the present invention can be used in various types of ink jet printers (such as Lexmark® Model Z51, Lexmark® Model Z31, and Lexmark® Model Z11, Lexmark® Photo Jetprinter 5770, or Kodak® PPM200).
For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
The present invention comprises TSRs 10 (
With the introduction of CMOS logic, N-Well material was added for the ability to create PMOS transistors in the CMOS logic blocks. N-Well is one of the most resistive materials on Lexmark CMOS print head chips and has a larger temperature coefficient than AlCu (see Table 1 below). Other implants listed are: NSD (n-type implant used for NMOS transistor source and drain areas), LDD (n-type implant used to form the lightly doped drain side of an n-type transistor), and PSD (p-type implant used for PMOS transistor source and drain areas).
By using N-Well for the TSR material, the following improvements over prior art metal TSR will result:
While N-Well is the preferred implant for TSRs, many implants (such as NSD, LDD, and PSD) used in the geometry shown in
The novel TSRs of the present invention can be used in various types of ink jet print heads, such as those shown in Lexmark's U.S. Pat. Nos. 6,398,333 and 6,382,758 (both incorporated herein by reference).
The novel TSRs of the present invention can be produced in a print head chip by the following method: Ion implantation of donor or acceptor atoms, followed by a thermal diffusion cycle, or by any standard method for producing MOS print head chips known to those of ordinary skill in this art.
The print head chip 120 of the present invention will typically contain 1-1000 TSRs 10 of the present invention. Each of these TSRs (when made of N-well material) can be, for example, 6-1000 μm wide by 6-100,000 μm long by 1-2 μm thick. Each of these TSRs (when made of NSD material) can be, for example, 2-1000 μm wide by 2-100,000 μm long by 0.4-0.8 μm thick. Each of these TSRs (when made of LDD material) can be, for example 2-1000 μm wide by 2-100,000 μm long by 0.2-0.4 μn thick. Each of these TSRs (when made of PSD material) can be, for example, 2-1000 μm wide by 2-100,000 μm long by 0.4-0.8 μm thick.
Aside from the novel TSRs of the present invention, print head chip 110 can be the same as chip 10 of Lexmark's U.S. Pat. Nos. 6,540,334; 6,398,346; 6,357,863; 5,984,455; 5,942,900.
The present invention includes an inkjet print head chip 110 having MOS logic blocks (CMOS, NMOS, or PMOS logic blocks), resistor elements to heat the chip, and a controller of the resistor elements and temperature sense resistors 10 implanted in the chip, the temperature sense resistors 10 being operatively connected to the controller of the resistor elements to enable the controller to monitor the chip temperature to control the resistor elements to heat the chip. For elements of the present invention not shown herein, see one or more of the U.S. patents mentioned herein (e.g., Lexmark U.S. Pat. No. 6,299,273), all of which are incorporated herein by reference.
Parts List:
The following is a list of parts and materials suitable for use in the present invention:
All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise.
The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
