Structure with photodiode, high electron mobility transistor, surface acoustic wave device and fabricating method of the same

1. Field of the Invention

The present invention relates to an integrated fabricating method of a structure with a photodiode, a high electron mobility transistor (HEMT) and a surface acoustic wave (SAW) device.

2. Description of the Prior Art

Photodiodes are light detectors that can convert light into current or voltage signals. They can output corresponding analog electrical signals or be used in controlling switches and processing digital signals based on the degree of light received. An HEMT is a kind of field effect transistor, which uses two materials with different energy gaps to form a heterojunction to provide a channel for carriers. Compared with traditional transistors, the HEMT has higher electron speed and electron density, so it can be used to increase speed of switch on or off. A surface acoustic wave filter (SAW Filter) can be widely used in various wireless communication systems, TV sets, VCRs and GPS receivers. Its main function is to filter out noise. The SAW Filter is easier to install than traditional filters.

However, with the shrinking demand for semiconductor chips, integration of circuits can increase component integration and reduce process steps. In addition, because the size of the chip becomes smaller, the distance of electron movement is reduced, so the speed of the chip can also be increased.

In view of this, the present invention provides an integrated process and structure having a photodiode, an HEMT and an SAW device to decrease fabricating cost and integrate devices on a chip.

According to a preferred embodiment of the present invention, a photodiode, an HEMT and an SAW device includes a photodiode including a first III-V semiconductor layer, a first N-type III-V semiconductor layer, a multi-quantum well (MQW) layer, a second III-V semiconductor layer, a P-type III-V semiconductor layer and a first electrode disposed from bottom to top. A second electrode is disposed on and contacts the first N-type III-V semiconductor layer. An HEMT includes a channel layer. An active layer is disposed on the channel layer. A P-type gate is disposed on the active layer. A gate electrode is disposed on and contacts the P-type gate. Two source/drain electrodes are respectively disposed at two sides of the P-type gate, wherein the two source/drain electrodes are embedded within the active layer and the channel layer. Schottky contact is between the first electrode and the P-type III-V semiconductor layer, and between the gate electrode and the P-type gate, Ohmic contact is between the second electrode and the first N-type III-V semiconductor layer, between one of the two source/drain electrodes and the active layer and between the other one of two source/drain electrodes and the active layer.

According to another preferred embodiment of the present invention, a fabricating method of a structure with a photodiode, an HEMT and an SAW device includes providing a substrate which is divided into a photodiode region and a transistor region. Later, a first III-V semiconductor layer is formed to cover the substrate. Next, two first recesses is formed to be embedded into the first III-V semiconductor layer within the transistor region. Subsequently, an N-type III-V semiconductor layer and an MQW layer are formed to cover the first III-V semiconductor layer from bottom to top, wherein the N-type III-V semiconductor layer fills up the two first recesses. After that, the N-type III-V semiconductor layer on a top surface of the first III-V semiconductor layer and the MQW layer on the top surface of the first III-V semiconductor layer are removed. After removing the N-type III-V semiconductor layer and the MQW layer on the top surface of the first III-V semiconductor layer, a second III-V semiconductor layer and a P-type III-V semiconductor material layer are formed from bottom to top to stack within the photodiode region and the transistor region. Next, part of the P-type III-V semiconductor material layer is removed, wherein the P-type III-V semiconductor material layer remaining within the photodiode region becomes a P-type semiconductor layer, and the P-type III-V semiconductor material layer remaining within the transistor region becomes a P-type gate. Later, two first conductive layers are respectively formed to cover the P-type III-V semiconductor material layer and the P-type gate. Then, two second recesses are respectively formed in each of the first recesses. Finally, three second conductive layers are formed, wherein two of the three second conductive layers respectively fill in the two second recesses, one of the three second conductive layers contacts the N-type III-V semiconductor layer within the photodiode region.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

FIG. 1 to FIG. 10 depict a fabricating method of a structure with a photodiode, an HEMT and an SAW device according to a preferred embodiment of the present invention, wherein:

FIG. 1 depicts a substrate divided into a photodiode region, a transistor region and an SAW region;

FIG. 2 depicts a fabricating stage following FIG. 1 ;

FIG. 3 depicts a fabricating stage following FIG. 2 ;

FIG. 4 depicts a fabricating stage following FIG. 3 ;

FIG. 5 depicts a fabricating stage following FIG. 4 ;

FIG. 6 depicts a fabricating stage following FIG. 5 ;

FIG. 7 depicts a fabricating stage following FIG. 6 ;

FIG. 8 depicts a fabricating stage following FIG. 7 ;

FIG. 9 depicts a fabricating stage following FIG. 8 ; and

FIG. 10 depicts a fabricating stage following FIG. 9 .

FIG. 1 to FIG. 10 depict a fabricating method of a structure with a photodiode, a high electron mobility transistor (HEMT) and a surface acoustic wave (SAW) device according to a preferred embodiment of the present invention.

As shown in FIG. 1 , a substrate 10 is provided. The substrate 10 can be a silicon substrate, a germanium substrate, a gallium arsenide substrate, a silicon germanium substrate, an indium phosphide substrate, a gallium nitride substrate, a silicon carbide substrate or a silicon-on-insulator. The substrate 10 is divided into a photodiode region A, a transistor region B and an SAW region C. Next, a first III-V semiconductor layer 12 a is formed to cover the photodiode region A, the transistor region B and the SAW region C on the substrate 10 . Later, two first recesses 14 a are formed to embed into the first III-V semiconductor layer 12 a within the transistor region B. The bottom of each of the first recesses 14 a doesn't penetrate the first III-V semiconductor layer 12 a . As shown in FIG. 2 , an N-type III-V semiconductor layer 12 n and a multi-quantum well (MQW) layer 16 are formed to cover the first III-V semiconductor layer 12 a from bottom to top. The N-type III-V semiconductor layer 12 n fills up the first recesses 14 a . The MQW layer 16 preferably includes a stack layer made of gallium nitride and indium gallium nitride. The top surface of the N-type III-V semiconductor layer 12 n and the top surface of the MQW layer 16 are parallel to the top surface of the substrate 10 .

As show in FIG. 3 , both of the N-type III-V semiconductor layer 12 n and the MQW layer 16 on the top surface of the first III-V semiconductor layer 12 a within the transistor region B and the SAW region C are removed. That is, only the N-type III-V semiconductor layer 12 n and the MQW layer 16 within the photodiode region A and the N-type III-V semiconductor layer 12 n within the first recesses 14 a remain. As shown in FIG. 4 , a second III-V semiconductor layer 12 b and a P-type III-V semiconductor material layer 12 p are formed from bottom to top to stack within the photodiode region A, the transistor region B and the SAW region C. In details, the second III-V semiconductor layer 12 b within the photodiode region A contacts the MQW layer 16 . The second III-V semiconductor layer 12 b within the transistor region B contacts the first III-V semiconductor layer 12 a and the N-type III-V semiconductor layer 12 n within the first recesses 14 a . The second III-V semiconductor layer 12 b within the SAW region C contacts the first III-V semiconductor layer 12 a . Moreover, the first III-V semiconductor layer 12 a , the N-type III-V semiconductor layer 12 n , the MQW layer 16 , the second III-V semiconductor layer 12 b and the P-type III-V semiconductor material layer 12 p are preferably formed by epitaxial processes.

As shown in FIG. 5 , the P-type III-V semiconductor material layer 12 p is patterned to remove part of the P-type III-V semiconductor material layer 12 p . In this way, the P-type III-V semiconductor material layer 12 p remaining within the photodiode region A becomes a P-type semiconductor layer 12 p 1 , and the P-type III-V semiconductor material layer 12 p remaining within the transistor region B becomes a P-type gate 12 p 2 . The P-type III-V semiconductor material layer 12 p within the SAW region C is entirely removed. The P-type semiconductor layer 12 p 1 only covers part of the second III-V semiconductor layer 12 b within the photodiode region A. The P-type gate 12 p 2 is between the two first recesses 14 a . Next, a first conductive material layer 18 is formed to conformally cover the P-type semiconductor layer 12 p 1 , the P-type gate 12 p 2 and the second III-V semiconductor layer 12 b . The first conductive material layer 18 is preferably formed by a deposition process. The first conductive material layer 18 is preferably Schottky metal and the Schottky metal includes a stacked layer formed by TiN/Al/TiN, Ni/Au, W/Au or Ni/Ag.

As shown in FIG. 6 , the first conductive material layer 18 is patterned to separate the first conductive material layer 18 into three first conductive layers 18 a / 18 b / 18 c . The first conductive material layer 18 can be patterned by an etching process. Later, the first III-V semiconductor layer 12 a and the second III-V semiconductor layer 12 b are etched to form two recesses 20 near an edge of the transistor region B. Then, an insulating layer 22 fills into the recesses 20 to isolate the transistor region B from other regions. The first III-V semiconductor layer 12 a within the transistor region B will serve as a channel layer for an HEMT afterwards. The second III-V semiconductor layer 12 b within the transistor region B will serve as an active layer for the HEMT afterwards. Moreover, three first conductive layer 18 a / 18 b / 18 c respectively cover and contact the P-type III-V semiconductor layer 12 p 1 , the P-type gate 12 p 2 and the second III-V semiconductor layer 12 b within the SAW region C. The first conductive layer 18 a contacting the P-type III-V semiconductor layer 12 p 1 within the photodiode region A will serve as a first electrode for a photodiode. The first conductive layer 18 b contacting the P-type gate 12 p 2 within the transistor region B will serve as a gate electrode for the HEMT. The first conductive layer 18 c contacting the second III-V semiconductor layer 12 b within the SAW region C will serve as an electrode for an SAW device.

As shown in FIG. 7 , a protective layer 24 is formed to conformally cover the three first conductive layers 18 a / 18 b / 18 c , the N-type III-V semiconductor layer 12 n and the second III-V semiconductor layer 12 b . Next, the protective layer 24 , the second III-V semiconductor layer 12 b and the MQW layer 16 within the photodiode region A are etched and the second III-V semiconductor layer 12 b and the first III-V semiconductor layer 12 a within the transistor region B are etched. In this way, the second III-V semiconductor layer 12 b and the MQW layer 16 not covered by the first conductive layer 18 a within the photodiode region A are removed and two second recesses 14 b are respectively formed within the first recesses 14 a . The second recesses 14 b extend into the second III-V semiconductor layer 12 b and the protective layer 24 . The first conductive layer 18 c and the protective layer 24 within the SAW region C are not etched. Now, part of the N-type III-V semiconductor layer 12 n within the photodiode region A is exposed, and the N-type III-V semiconductor layer 12 n remains around the bottom of the second recesses 14 b.

As shown in FIG. 8 , three second conductive layers 26 a / 26 b / 26 c are formed. Two of the second conductive layers 26 b / 26 c respectively fill in the two second recesses 14 b , one of the second conductive layers 26 a contacts the N-type III-V semiconductor layer 12 n within the photodiode region A. The second conductive layers 26 a / 26 b / 26 c are ohmic metal, and the ohmic metal includes a stacked layer of Ti/Al/TiN, Si/Ti/Al/TiN, Si/Ti/Ta/Al/TiN or Si/Ti/Al/Ti/Au. The second conductive layers 26 b / 26 c within the second recesses 14 b will serve as source/drain electrodes of the HEMT. The second conductive layer 26 a within the photodiode region A will serve as a second electrode for the photodiode.

As shown in FIG. 9 , a dielectric layer 28 is formed to cover the photodiode region A, the transistor region B and the SAW region C entirely. Next, numerous contact plugs 30 are formed to penetrate the dielectric layer 28 . The contact plugs 30 respectively contact the first conductive layer 18 a and the second conductive layer 26 a within the photodiode region A, and contact the second conductive layers 26 b / 26 c within the transistor region B and the first conductive layer 18 c within the SAW region C. As shown in FIG. 10 , part of the dielectric layer 28 and part of the protective layer 24 within the photodiode region A and the SAW region C are removed to expose part of the first conductive layer 18 a within the photodiode region A and expose part of the first conductive layer 18 c within the SAW region C. Next, the first conductive layer 18 c within the SAW region C is etched to form an interdigital transducer 18 c 1 . Now, a structure 100 with a photodiode, an HEMT and an SAW device of the present invention is completed.

As shown in FIG. 10 , the structure 100 with a photodiode, an HEMT and an SAW device includes a photodiode P, an HEMT H and an SAW device S. The photodiode P includes a first III-V semiconductor layer 12 a , a first N-type III-V semiconductor layer 12 n , a MQW layer 16 , a second III-V semiconductor layer 12 b , a P-type III-V semiconductor layer 12 p 1 and a first electrode (first conductive layer 18 a ) disposed from bottom to top. A second electrode (second conductive layer 26 a ) is disposed on and contacts the first N-type III-V semiconductor layer 12 n . The HEMT H includes a channel layer (first III-V semiconductor layer 12 a ) and an active layer (second III-V semiconductor layer 12 b ) disposed on the channel layer. A P-type gate 12 p 2 is disposed on the active layer. A gate electrode (first conductive layer 18 b ) is disposed on and contacts the P-type gate 12 p 2 . Two source/drain electrodes (second conductive layers 26 b / 26 c ) are respectively disposed at two sides of the P-type gate 12 p 2 . The two source/drain electrodes are embedded within the active layer and the channel layer. The two N-type III-V semiconductor layers 12 n are embedded within the channel layer. Each of the N-type III-V semiconductor layers 12 n respectively contacts one of the source/drain electrodes (second conductive layers 26 b / 26 c ).

The SAW device S includes a piezoelectric layer 30 . The piezoelectric layer 30 is formed by the first III-V semiconductor layer 12 a and the second III-V semiconductor layer 12 b . An interdigital transducer 18 c 1 is disposed on and contacts the piezoelectric layer 30 . It is noteworthy that Schottky contact is between the first electrode (first conductive layer 18 a ) and the P-type III-V semiconductor layer 12 p 1 , between the gate electrode (first conductive layer 18 b ) and the P-type gate 12 p 2 , and between the interdigital transducer 18 c 1 and the piezoelectric layer 30 . Ohmic contact is between the second electrode (second conductive layer 26 a ) and the N-type III-V semiconductor layer 12 n , between the source/drain electrode (second conductive layers 26 b ) and the active layer (second III-V semiconductor layer 12 b ) and between the source/drain electrode (second conductive layers 26 c ) and the active layer.

Moreover, the N-type III-V semiconductor layer 12 n of the photodiode P and N-type III-V semiconductor layer 12 n of the HEMT H are originally formed by the same material layer. Therefore, the N-type III-V semiconductor layer 12 n of the photodiode P and N-type III-V semiconductor layer 12 n of the HEMT H are of the same material. According to a prefer embodiment of the present invention, the N-type III-V semiconductor layer 12 n is N-type gallium nitride. Furthermore, the P-type III-V semiconductor layer 12 p 1 and the P-type gate 12 p 2 are made of the P-type III-V semiconductor material layer 12 p , therefore, the P-type III-V semiconductor layer 12 p 1 and the P-type gate 12 p 2 are of the same material. According to a prefer embodiment of the present invention, the P-type III-V semiconductor layer 12 p 1 and the P-type gate 12 p 2 are P-type gallium nitride. The source/drain electrodes (second conductive layers 26 b / 26 c ) and the second electrode (second conductive layers 26 a ) are all second conductive layers, therefore they have the same material. According to a prefer embodiment of the present invention, the source/drain electrodes and the second electrode are made of ohmic metal, and the ohmic metal includes a stacked layer of Ti/Al/TiN, Si/Ti/Al/TiN, Si/Ti/Ta/Al/TiN or Si/Ti/Al/Ti/Au. The first electrode (first conductive layer 18 a ), the gate electrode (first conductive layer 18 b ), the interdigital transducer 18 c 1 are all made of the first conductive material layer 18 . Therefore, the first electrode, the gate electrode and the interdigital transducer 18 c 1 are all made of the same material. According to a prefer embodiment of the present invention, the first electrode, the gate electrode, the interdigital transducer 18 c 1 are made of Schottky metal and the Schottky metal includes a stacked layer of TiN/Al/TiN, Ni/Au, W/Au or Ni/Ag.

Moreover, the first III-V semiconductor layer 12 a is gallium nitride. The second III-V semiconductor layer 12 b is aluminum gallium nitride. The MQW layer 16 preferably includes a stacked layer made of gallium nitride and indium gallium nitride.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.