1. Technical Field
The present disclosure relates to the field of radio frequency power devices, and more specifically, to a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate and the production method thereof.
2. Description of Related Art
The high electron mobility transistor (HEMT) is widely regarded as one of the most promising high-speed electronic devices. With advantageous features, such as ultra high speed, low power consumption and low noise level (especially at low temperature), the HEMT device is capable of satisfying the special needs of ultra high-speed computers, signal processing, satellite communications, etc., in purpose and hence receives much attention. As a new generation of microwave and millimeter-wave devices, the HEMT has unraveled advantages in frequency, gain and efficiency. After more than a decade of development, the HEMT device possesses the properties of excellent microwave and millimeter wave and becomes a main device for low-noise microwave and millimeter-wave amplifiers in fields like 2˜100 GHz satellite communications and radio astronomy. Moreover, the HEMT device is also used for making the core parts of microwave mixers, oscillators and broadband traveling-wave amplifiers.
GaN-based HEMT radio frequency power devices in the prior art are mostly produced by using the gate-last process. The process flow of the production mainly includes: first, make a source and a drain; photo-etch ohmic contact holes, form a multi-layer electrode structure by electron-beam evaporation, form source-drain contact by use of the lift-off process, and form good source-drain ohmic contact at 900° C. in 30 seq thermal annealing (RTA) equipment under the protection of argon gas; next, photo-etch the regions that need to be etched away, and etch steps by using a piece of reactive ion beam etching (RIE) equipment while introducing boron chloride; finally, form Schottky barrier gate metal by using photo-etching, electro-beam evaporation and lift-off processes again. However, as the device becomes smaller and smaller, it is difficult to implement accurate position alignment between the gate and the source, drain of the HEMT device by means of the gate-last process, resulting in parameter drift of products.
The object of the present disclosure is to provide a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate and the production method thereof so as to implement the self-position alignment between the gate and the source, drain of radio frequency power devices, reduce parameter drift of products and enhance the electrical properties of radio frequency power devices.
The present disclosure provides a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate, comprising:
an AlGaN buffer layer, a GaN channel layer and an AlGaN isolating layer formed in turn on the substrate;
and a gate dielectric layer formed on the AlGaN isolating layer;
a gate stack region formed on the gate dielectric layer, including a gate and a passivating layer on the gate;
a first gate sidewall formed on either side of the gate stack region;
a drain and a source formed respectively on the outer side of the first gate sidewalls on both sides of the gate stack region;
a second gate sidewall formed between the first gate sidewall close to one side of the drain and the drain.
Furthermore, a field plate is formed on the first gate sidewall close to the drain, wherein the field plate is connected with the source and extends over the second gate sidewall and the passivating layer on the gate along the length of the current channel of the device.
Furthermore, the source and the drain are located on the AlGaN isolating layer and formed by alloy materials.
Furthermore, the source and the drain are located in the AlGaN isolating layer and formed by the silicon iron doped region in the AlGaN isolating layer.
Furthermore, the source and the drain are located on the GaN channel layer and formed by silicon doped GaN or AlGaN materials.
The present disclosure also provides a method for producing the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate as described above, and the specific steps are as follows:
deposit an AlGaN buffer layer, a GaN channel layer and an AlGaN isolating layer in turn on the substrate; etch the AlGaN isolating layer, the GaN channel layer and the AlGaN buffer layer in turn with a photo-resist as the etching stop layer to form an active region, followed by removal of the resist;
deposit the first layer of insulating film, the first layer of conductive film and the second layer of insulating film in turn on the exposed surface of the structure formed;
define the location of the gate stack region of the device by photo-etching and development;
etch away the second layer of insulating film and the first layer of conductive film exposed in turn with a photo-resist as the etching stop layer, followed by removal of the resist, in this way the remaining first layer of conductive film and second layer of insulating film form the gate stack region which comprises the gate of the device and the passivating layer on the gate;
deposit the third layer of insulating film on the exposed surface of the structure formed, and etch the third layer of insulating film to form a first gate sidewall on either side of the gate stack region;
deposit a layer of polysilicon on the exposed surface of the structure formed, etch back the polysilicon formed, but the polysilicon at the source is not etched away;
deposit the fourth layer of insulating film on the exposed surface of the structure formed, and etch the fourth layer of insulating film to form the second gate sidewall on the side of the gate stack region close to the drain;
etch away the remaining polysilicon, and continue to etch away the first layer of insulating film exposed.
The production method of a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate also comprises:
form a pattern by the photo-etching process to define the locations of the source and the drain respectively;
form the source and drain of the device by the lift-off process and the alloying process;
form a field plate on the first gate sidewall close to the drain, wherein the field plate is connected with the source and extends over the second gate sidewall and the passivating layer on the gate along the length of the current channel of the device.
The production method of a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate also comprises:
form a pattern by the photo-etching process and expose the locations of the source and the drain by means of a pattern;
implant silicon irons into the AlGaN isolating layer by the iron implanting process to form the source and drain of the device;
form a field plate on the first gate sidewall close to the drain, wherein the field plate is connected with the source and extends over the second gate sidewall and the passivating layer on the gate along the length of the current channel of the device.
The production method of a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate also comprises:
continue to etch away the exposed AlGaN isolating layer to expose the GaN channel layer formed;
form a pattern by the photo-etching process and expose the locations of the source and the drain by means of a pattern;
grow silicon doped GaN or AlGaN by the epitaxy process to form the source and drain of the device on the exposed GaN channel layer;
form a field plate on the first gate sidewall close to the drain, wherein the field plate is connected with the source and extends over the second gate sidewall and the passivating layer on the gate along the length of the current channel of the device.
The production method of a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate, wherein the first layer of insulating film is any one of silicon oxide, silicon nitride, hafnium oxide or Al2O3, while the second layer of insulating film, the third layer of insulating film and the fourth layer of insulating film are any one of silicon oxide or silicon nitride.
The production method of a radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate, wherein the first layer of conductive film is chromium, nickel or tungsten-containing alloy.
In the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure, gate sidewalls are utilized to implement the self-position alignment of the source, drain and gate, thereby reducing parameter drift of products; besides, the source and drain of the device can be formed directly by the alloying process, the iron implanting process or epitaxy process after formation of the gate since the gate is protected by the passivating layer, thereby reducing the parasitic source-drain resistances and enhancing the electrical properties of the radio frequency power device.
The present disclosure is further detailed by the embodiments in combination with the drawings. For the convenience of description, the thickness of the layers and regions is increased or reduced in the figures, so those indicated are not the actual sizes. Despite the fact that these figures do not reflect the actual size of the device exactly, they completely reflect the mutual relationship in position among regions and constituent structures, especially the upper and lower as well as adjacent relationships among the constituent structures.
In the embodiment of the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure as shown in
In the embodiment of the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure as shown in
In the embodiment of the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure as shown in
Multiple radio frequency power devices for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure can make up a radio frequency power device array.
The production methods of the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate provided by the present disclosure and the radio frequency power device array consisting of the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate are the same. The following is to describe the process flow for fabricating the structure of the radio frequency power device according to the present disclosure.
First, as shown in
The substrate in the embodiment comprises a base 200 and a GaN buffer layer 201 formed on the base 200, and the base 200 can be silicon, SiC or Al2O3.
Next, deposit the first layer of insulating film 205, the first layer of conductive film and the second layer of insulating film in turn on the exposed surface of the structure formed; deposit a layer of photo-resist on the second layer of insulating film, and define the location of the device's active region by masking, exposure and development; etch away the second layer of insulating film and the first layer of conductive film exposed in turn with a photo-resist as the etching stop layer, in this way the remaining first layer of conductive film and second layer of insulating film form the gate stack region which comprises the gate 206 of the device and the passivating layer 207 on the gate; after removal of the resist, the structure is as shown in
The first layer of insulating film 205 can be silicon oxide, silicon nitride, hafnium oxide or Al2O3, and the thickness is preferably 8 nm as the gate dielectric layer. The gate 206 can be chromium, nickel or tungsten-containing alloy, such as nickel-gold alloy, palladium-gold alloy, platinum-gold alloy, nickel-platinum alloy or nickel-palladium alloy. The passivating layer 207 can be silicon dioxide or silicon nitride.
Next, deposit the third layer of insulating film on the exposed surface of the structure formed, and etch back the third layer of insulating film formed to form a first gate sidewall 208 on either side of the gate stack region, as shown in
Next, deposit a layer of polysilicon film 210 on the exposed surface of the structure formed, as shown in
In a GaN radio frequency power device array, the polysilicon is etched away except that at the location of the source when etching the polysilicon film 210 by controlling the distance between gates.
Next, deposit the fourth layer of insulating film on the exposed surface of the structure formed, and etch the fourth layer of insulating film formed to form a second gate sidewall 209 on one side of the gate stack region, as shown in
Next, deposit a layer of photo-resist on the exposed surface of the structure formed, form a pattern by masking, exposure and development, and expose the locations of the source and the drain by mean of a pattern, as shown in
Next, grow silicon doped GaN or AlGaN by the epitaxy process to form the source 212 and the drain 211 of the device on the exposed GaN channel layer 203, remove the photo-resist and polysilicon GaN, as shown in
Finally, deposit a new layer of photo-resist on the exposed surface of the structure formed, define the location of the field plate, source and drain of the device by masking, exposure and development, deposit the second layer of conductive film, wherein the second layer of conductive film can be titanium-aluminium alloy, nickel-aluminium alloy, nickel-platinum alloy or nickel-gold alloy, remove the second layer of conductive film deposited on the photo-resist by use of the lift-off process known in the field and keep the second layer of conductive film not deposited on the photo-resist to form the field plate 214 of the device on the first gate sidewall 208 close to one side of the drain 211, wherein the field plate 214 is connected with the source 212, and form the contact 213 of the drain for connecting the drain to the external electrode, as shown in
The structure of the radio frequency power device array shown in
In the production method of the radio frequency power device array described in
Next, implant silicon irons into the AlGaN isolating layer 204 by the iron implanting process to form the source 212 and the drain 211 of the device, and carry out rapid thermal processing after removal of the photo-resist, as shown in
Finally, deposit a new layer of photo-resist on the exposed surface of the structure formed, define the location of the field plate, source and drain of the device by masking, exposure and development, and then deposit the second layer of conductive film, wherein the second layer of conductive film can be titanium-aluminium alloy, nickel-aluminium alloy, nickel-platinum alloy or nickel-gold alloy, remove the second layer of conductive film deposited on the photo-resist by use of the lift-off process known in the field and keep the second layer of conductive film not deposited on the photo-resist to form the field plate 214 of the device on the first gate sidewall close to one side of the drain 211, wherein the field plate 214 is connected with the source 212, and form the contact 213 of the drain for connecting the drain to the external electrode, as shown in
The structure of the radio frequency power device array shown in
In the production method of the radio frequency power device array described above, it is workable to not carry out the iron implanting process after etching away the remaining polysilicon film 210 and continuing to etch away the first layer of insulating film 205 exposed to expose the AlGaN isolating layer 204; deposit a layer of photo-resist on the exposed surface of the structure formed instead, and form a pattern by masking, exposure and development to define the locations of the source and the drain, as shown in
Next, form the source 212 and the drain 211 of the device on the AlGaN isolating layer 204 by use of the lift-off process and the alloying process, as shown in
finally, deposit a new layer of photo-resist on the exposed surface of the structure formed, define the location of the field plate, source and drain of the device by masking, exposure and development, deposit the second layer of conductive film, wherein the second layer of conductive film can be titanium-aluminium alloy, nickel-aluminium alloy, nickel-platinum alloy or nickel-gold alloy; and then remove the second layer of conductive film deposited on the photo-resist by use of the lift-off process known in the field and keep the second layer of conductive film not deposited on the photo-resist to form the field plate 214 of the device on the first gate sidewall close to one side of the drain 211, wherein the field plate 214 is connected with the source 212, and form the contact 213 of the drain for connecting the drain to the external electrode, as shown in
The structure of the radio frequency power device array shown in
As described above, many other embodiments with great difference can be formed without deviating from the spirit of the present disclosure. It should be understood that the present disclosure is not limited to the specific embodiments described in the specification except those limited by the claims attached.
In the radio frequency power device for implementing asymmetric self-alignment of the source, drain and gate according to the present disclosure, gate sidewalls are utilized to implement the self-position alignment of the source, drain and gate, thereby reducing parameter drift of products; besides, the source and drain of the device can be formed directly by the alloying process, the iron implanting process or epitaxy process after formation of the gate since the gate is protected by the passivating layer, thereby reducing the parasitic source-drain resistances and enhancing the electrical properties of the radio frequency power device.
Number | Date | Country | Kind |
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201310098145.5 | Mar 2013 | CN | national |
201310098164.8 | Mar 2013 | CN | national |
201310098173.7 | Mar 2013 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2014/074011 | 3/25/2014 | WO | 00 |