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Difference between revisions of "Viability of 3-D printing semiconductors of Zinc Antimonide in transistors"

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===Introduction===
 
===Introduction===
Our team is investigating a way to print semiconductor transistors using 3D-printing technology. Specifically using  [http://en.wikipedia.org/wiki/Zinc_antimonide Zinc Antimonide] (ZnSb) as the semiconducting material for both the N-type and P-type [http://en.wikipedia.org/wiki/Semiconductor semiconductor] material for use in the [http://en.wikipedia.org/wiki/Transistor transistor]. The transistor itself is a small, simple component in modern electronic devices which can be built upon to create a wide variety of useful "smart" devices.
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Our team is investigating a way to print semiconductor transistors using 3D-printing technology. Specifically using  [http://en.wikipedia.org/wiki/Zinc_antimonide Zinc Antimonide] (ZnSb) as the semiconducting material for both the N-type and P-type [http://en.wikipedia.org/wiki/Semiconductor semiconductor] material for use in the [http://en.wikipedia.org/wiki/Transistor transistor]. The transistor itself is a small, relatively simple component used in modern electronic devices which can be built upon to create a wide variety of useful "smart" devices. Some possibilities include smart materials that can sense their environment, respond to signals the potential to provide processing capabilities, all within a package that could be readily generated in a home or hobby environment.
  
 
===Background===
 
===Background===

Revision as of 15:10, 16 October 2013

Asi.png This page was part of a project for MY3701 -- an MTU class on semiconductors.

This page is now open edit -- please fix mistakes or feel free to leave comments using the discussion tab.


Introduction

Our team is investigating a way to print semiconductor transistors using 3D-printing technology. Specifically using Zinc Antimonide (ZnSb) as the semiconducting material for both the N-type and P-type semiconductor material for use in the transistor. The transistor itself is a small, relatively simple component used in modern electronic devices which can be built upon to create a wide variety of useful "smart" devices. Some possibilities include smart materials that can sense their environment, respond to signals the potential to provide processing capabilities, all within a package that could be readily generated in a home or hobby environment.

Background

  • Team
  • Brief description of the semiconductor material with a link to the manufacturer(s) or suppliers

Benefits of 3D Printing

The core benefit of using the 3D printing approach of electronic device creation is the flexibility that is inherent to the process. Provided suitable materials and schematics are available it is possible to build any combination of devices. The transistor is a small but very potent part of this flexibility. Once a suitable transistor is designed, numerous electronic circuits of interest can then be fabricated such as logic gates, amplifying circuits and device control switches. Not only can these devices be created, they can be scaled to suit specific needs.

It would be possible then for a suitably equipped 3D printer to not only be able to print "smart" parts that could electronically interface with each other, but to also build control circuits used to run the printers. Some applications could include building control board for running newer versions of 3D printers that not only handle the operational control functions of running stepper motors and controlling current to the extrusion head, but also sensing capabilities that could be directly integrated into the components used to build the printers. integrating sensing circuits into printed components would allow for feedback signals that could permit higher quality parts to be printed with less waste due to part scrapping.

The Transistor

Transistors penetrate all levels of our society; they appear in our homes, our workplaces, our kitchens, our pockets. They have helped us go into space and into the depths of the ocean. They form the basis of any "smart" device. A transistor has three terminals: the base, the emitter, and the collector. Transistors control current flow; a small current in the base controls a large current running through the collector and emitter.[1]
Figure 1: Simple diagram of a Bi-polar transistor
When the current flows into the base, as is shown in Figure 1, current will flow from the collector to the emitter, as is shown. When current flows the other direction, current will only flow in the other direction.

Method of Printing Transistors

The bulk of the 3D printed part can be constructed using traditional extrusion methods to build up the surfaces and component as desired. The printing of the transistor and associated trace leads would require the creation of a flat smooth surface. To achieve this desired surface after creating the plane where the transistor is to be located, several layers of polyurethane should be used to fill in small surface defects left behind by previous passes with the extrusion head.

The simplest solution to applying the polyurethane is to use a modified Ink-Jet printing cartridge. The purpose of the inkjet head is to provide a controllable fine droplet pattern similar to that achieved by a spray head used for coating surfaces with polyurethane. The layers should be applied in successive passes avoiding delays between each layer to ensure that the layers fully bond to each other and to allow the liquid polyurethane to "float" the surface to achieve as smooth and flat a surface as desired. Because the method relies on the polyurethane to "float" the surface, the applying of transistors is limited to work in the flat plane that is normal to the pull of gravity. This will require some care in the setup of the printer itself as the liquid polyurethane may tend to run if applied to a surface that is not level. This may be somewhat controlled by building up an extruded dam of material prior to applying the polyurethane forming a lake or pool for the polyurethane to cure in

Once the flat surface is achieved the ZnSb semiconductor can be applied to create the semiconductor N-P-N junction. Additionally silver ink [2] may be applied to create conductive traces to carry the signals to and from the transistor. Both the silver ink and the transistor material will need to be cured after application. One possible method of curing the material is the use of a small radiant heating element fitted to the extrusion carriage so that the heat may be applied only where desired to avoid unnecessary thermal input back into the previously extruded material.

After the thermal treatment of the material several additional coatings of polyurethane may be applied to protect the circuit traces and the transistor junction itself. In much the same way that traditional printed circuit boards use vias to provide electrical connection between layers, portions of the circuit may be "masked" off to allow for an electrical equivalent. In places where it is desired to provide interconnection between layers the polyurethane may be excluded during the recoating process.

After the new layer is applied an additional transistor and circuit traces may be applied to increase the density of electrical components within the device. The limitation here is the possibility of electrical interference from adjacent layers due to induced signals from one layer to the next. This along with concerns of dissipating thermal energy will require some ingenuity and experimentation on the part of the daring user.

Materials

Cost

Material Source Cost MSDS
Zinc ScienceLab $0.32/g [1]
Antimony [2] $2.19/g [3]
α-terpineol ScienceLab $0.20/ml [4]
DisperBYK-110 BYK TBA TBA
Copper Granular ScienceLab $0.71/g [5]
Tellurium Powder ScienceLab $1.57/g [6]
Conductive Silver Ink iimak TBA [7]
Verowhite polyeurathane Redeye TBA [8]

Steps of Synthesizing

P-Type ZnSb

Doping the ZnSb with copper will create a p-type material. To do this a combination of heating, quenching, and ball-mill crushing will be implemented. All the granular metals (Zinc, Antimony, and Copper) will be together in a container and placed in a furnace. With the furnace set at 1073K for 24 hours, with the occasional rocking. The granular pieces after the furnace will be left to cool at room temperature. Using a ball-milling machine with an argon atmosphere for 1-1.5 hours to finely crush the granulars, similar to the process in [3]. The atomic weight percent of copper needed to have efficient doping is 0.1 at%, as carrier concentration is a diminishing return as copper concentration increases [3]. To get a printable viscosity a process similar to [4], for this we will use the chemicals α-terpineol and DisperBYK-110 which are the same as [3]. For every 10 grams crushed ZnSb 10 milliliters of α-terpineol will be used and 1 milliliter of DisperBYK-110 and make sure that it is mixed well.

N-Type ZnSb

Doping the ZnSb with Tellurium will create an n-type material. To get an n-type ZnSb is very difficult, but can be done. A study [5], shows that there has to be a certain atomic weight percent of Tellurium, which is 2.06at%. The process of creating the n-type ZnSb is to heat the the granular Zinc and Antimony with the powdered Tellurium at 923 in an ampoule then water quenching the ampoule. After opening the ampoule the materials will be ball-milled until finely crushed After the doping process the process for the P-Type ZnSb paste will be repeated with the α-terpineol at 10 milliliters get 10 grams of ZnSb and the 1 milliliter of DisperBYK-110.

Dia Workflow

Transitor creation workflow.png

Purification Methods

The raw materials purchased from ScienceLab.com are of acceptable minimum purity for the purpose of creating transistors. The minimum purity for each metal going into the semiconductor is listed in the table below.

Metal Purity
Zinc 99.8% (min)
Antimony 99% (min)
Copper 98% (approx)
Tellurium 99.5% (min)

Testing

As a method of testing the doping concentration of tellurium in the n-type zinc antimonide, a wafer is printed. It is then tested to find resistivity using a Signatone Manual Four Point Resistivity Probing Equipment fitted with an SP4 Four Point Probe Head[6]. Resistivity is used to find the doping density according to the following equation[7]:

\sigma=eN_{\it d}\mu_{\it e}

Where the inverse of the resistivity is \sigma, conductivity, e is the charge of an electron, \mu_{\it e} is the electron mobility, and N_{\it d} is the donor atom doping concentration.

The p-type ZnSb doping concentration can be determined using a similar method:

\sigma=eN_{\it a}\mu_{\it h}

Where the inverse of resisitivity is again \sigma,conductivity, e is the charge of a hole (same as the charge of an electron), \mu_{\it h} is the hole mobility, and N_{\it a} is the acceptor atom doping concentration.

Material Properties

N-type ZnSb

  • High ZnSb purity (post thermal curing)
  • Tellurium concentration: 2.06 at%
  • Homogeneous tellurium distribution

P-type ZnSb

  • High ZnSb purity (post thermal curing)
  • Copper concentration: ~0.1 at%
  • Homogeneous copper distribution

Characterization

One method found in previous experiments for characterizing ZnSb is X-ray diffraction[8] X-Ray diffraction shows the phase, as well as the inter-plainer spacing and size of the crystal lattice. Determination of the lattice parameter will show if there are interstitials or vacancies. [9] Unfortunately, this method does not work well for in-sit characterization. The best time for XRD is when the material is still in ink form. Because transistors are used for their electrical properties, simple electrical testing would be the best option for in-sit characterization.

Applications

The beauty behind the 3-D printer is it's flexibility and its ability to create nearly any shape from a computer generated image. This already allows for countless possibilities for use in the home. Now add in the ability to print transistors. Modern homes are already full of electronics, and nearly every one of them uses transistors. The simple power to print transistors to replace or modify parts of these electronics is noticeable.

If transistors are able to be printed, then it should be possible to print integrated circuits. With the ability to print chips in the home, anyone with the knowledge could create:

  • radios
  • remote controllers
  • simple memory/storage devices
  • simple computer/calculator parts
  • and more and more

The ability to print transistors in the home combined with open source designs offers many opportunities for exploring enthusiast and the practical homeowner alike.

OpenSCAD

The proposed semiconductor was drawn up using OpenSCAD. The basic design is that of a fairly simple NPN junction[10]. Implementation in real devices will likely require some experimentation on the part of the the end user to determine the optimal scaling of the device based on intended use.

In the two views of the device, the blue material corresponds to the p-type material, the red corresponds to the n-type material. The green sections are conductive traces intended to be made from a material capable of carrying a signal such as Xerox's Silver nano-particle ink[11] The teal circles are locations where the lead may be terminated to a contact or treated as a via to pass between different layers for increased device complexity options.


3D-NPN Isometric view.png
Top down view.png

OpenSCAD:Coding

Below is the OpenSCAD code used to generate the model:

//P-type
color([0,0,1])
cube([1,4,1]);
//RH-N-type
color([1,0,0])
translate([1,0,0])
cube([2,4,1]);
//LH-N-type
color([1,0,0])
translate([-2,0,0])
cube([2,4,1]);
//P-contact trace
union(){
color([0,1,0])
translate([0.25,-4,0])
cube([0.5,4,0.5]);
color([0,1,1])
translate([0.5,-4.5,0])
cylinder(h=0.5,r=1,$fn=100);
}
//RH-N-contact trace
union(){
color([0,1,0])
translate([3,1.75,0])
cube([3,0.5,0.5]);
color([0,1,0])
translate([6,-3.75,,0])
cube([0.5,6,0.5]);
color([0,1,1])
translate([6.3,-4.5,0])
cylinder(h=0.5,r=1,$fn=100);
}
//LH-N-contact trace
union(){
color([0,1,0])
translate([-5.0,1.75,0])
cube([3,0.5,0.5]);
color([0,1,0])
translate([-5.5,-3.75,,0])
cube([0.5,6,0.5]);
color([0,1,1])
translate([-5.25,-4.5,0])
cylinder(h=0.5,r=1,$fn=100);

OpenSCAD:STL Modeling

The link listed below is for the resulting .stl file for inclusion of the transistor in an actual device. Please note however that the model is scaled quite large using (mostly) integer sizes (mm) so that it can be readily scaled down depending on the application.

[Printable transistor]

Please see the description listed in the OpenSCAD section for material placements & types.

References

  1. Template:Http://www.allaboutcircuits.com/vol 3/chpt 4/1.html
  2. "Silver Ink to print Plastic Circuits". Xerox Corporation. http://www.xerox.com/innovation/news-stories/silverbullet/enus.html.
  3. 3.0 3.1 3.2 http://onlinelibrary.wiley.com/doi/10.1002/pssa.201127211/pdf
  4. http://www.sciencedirect.com/science/article/pii/S0040609011006778
  5. http://www.jim.or.jp/journal/e/pdf3/50/10/2473.pdf
  6. LucasLabs.com: Signatone
  7. S.O. Kasap. Principles of Electronic Materials and Devices, Third Edition, McGraw Hill, New Delhi, 2006, p. 389
  8. "Nanocrystalline ZnSb2O6: Hydrothermal synthesis, electronic structure and photocatalytic activity". Journal of Molecular Catalysis A: Chemical. http://www.sciencedirect.com/science/article/pii/S1381116911003505.
  9. Template:Culitty, B.D., and S.R. Stock. Elements of X-Ray Diffraction. 3rd Edition. Prentice Hall, 2001. Print.
  10. "Bipolar Junction transistor". Wikipedia Bipolar Transistors. http://en.wikipedia.org/wiki/Bipolar_junction_transistor.
  11. "Silver Ink to print Plastic Circuits". Xerox Corporation. http://www.xerox.com/innovation/news-stories/silverbullet/enus.html.

Contacts

Alisha Clark Robert Cooley Nathaniel Musser Michel Knuden
user:Alishac user:Rjcooley user:Namusser user:M.Knudsen