ISPSD 2016 28th International Symposium on Power Semiconductor Devices and ICs., Jun 12-16, 2016, Žofín Palace, Prague, Czech RepublicThe performance of a novel diode with characteristic trench shape is predicted by TCAD simulation. A novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process is proposed for a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced to a half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. The novel diode structure is a strong candidate when the simple fabrication process under development is established

Baba, Akiyoshi

Omura, Ichiro

Shiba, Yuji

Tsukuda, Masanori

Kyushu Institute of Technology of Academic Repository

Kyushu Institute of Technology Academic Repository
九州工業大学学術機関リポジトリ
TitleNovel 600 V Low Reverse Recovery Loss Vertical PiN Diodewith Hole Pockets by Bosch Deep Trench
Author(s)Tsukuda, Masanori; Baba, Akiyoshi; Shiba, Yuji; Omura,Ichiro
Issue Date2016-06
URL http://hdl.handle.net/10228/5737
RightsIEEE
Novel 600 V Low Reverse Recovery Loss Vertical 
PiN Diode with Hole Pockets by Bosch Deep Trench 
 
Masanori Tsukuda 
Green Electronics Research Institute, Kitakyushu,  
Asian Growth Research Institute 
1-8 Hibikino, Wakamatsu-ku, Kitakyushu, Japan  
tsukuda@grik.jp 
Akiyoshi Baba, Yuji Shiba and Ichiro Omura 
Kyushu Institute of Technology 
1-1 Sensui-cho, Tobata-ku, Kitakyushu, Japan  
 
 
Abstract— The performance of a novel diode with 
characteristic trench shape is predicted by TCAD simulation. A 
novel 600 V vertical PiN diode with hole pockets by the Bosch 
deep trench process is proposed for a better trade-off curve 
between reverse recovery loss and forward voltage. The reverse 
recovery loss is reduced to a half. In addition, the active chip size 
of the novel diode is reduced to two-thirds that of the 
conventional PiN diode in the same forward voltage. The novel 
diode structure is a strong candidate when the simple fabrication 
process under development is established. 
Keywords— diode; vertical; trench; Bosch; hole; reverse 
recovery loss 
I. 	Introduction:	Requirement	
for	novel	vertical	diode	
Efficiency improvement and the prevalence of high 
efficiency power electronics apparatus are key factors for 
efficient energy usage in our more electric-oriented society [1]. 
For these key factors, reverse recovery loss reduction (fast 
reverse recovery) at certain forward voltage and low cost are 
required for diodes in the power electronics apparatus.  
To meet these demands, diodes have made remarkable 
progress in recent decades and many technologies have been 
continuously studied to enable next-generation power 
electronics. 
Silicon diodes are superior to wide-bandgap diodes in the 
aspect of low cost (mass production technology). On the other 
hand, it was believed that the physical properties of silicon 
make it difficult to reduce reverse recovery loss any lower. To 
overcome the limitations of this silicon device, many 
researchers have endeavored to reduce reverse recovery loss 
by novel diode structure with hole pockets or deep trench [2-
12]. However, there is no simple and fast fabrication process 
for the diodes at present. 
We previously proposed a lateral SOI PiN diode with hole 
pockets as a novel diode structure to revise recovery loss 
reduction [13, 14]. Thanks to the waveform oscillation 
suppression with hole pockets, the diode successfully reduces 
reverse recovery loss to a half by the short current path (see 
Fig. 1). On the other hand, the cost of the lateral diode is 
predicted to be high because the diode with the thin Si layer 
requires a large chip size at a certain forward voltage (see Fig. 
2). It is about three times larger than conventional vertical 
diodes. Therefore, a vertical PiN diode with hole pockets is 
proposed with novel technology of the Bosch deep trench 
process [15]. 
 
 
Fig. 1. Simulated trade-off curves between reverse recovery loss and 
forward voltage of lateral PiN diode and conventional diode without 
oscillation waveform. 
 
 
 
 
Fig. 2. Simulated trade-off curves between active chip size and forward 
voltage of lateral PiN diode and conventional diode without oscillation 
waveform. 
II. Hole	pocket	shape	by	Bosch	
deep	trench	process	
The Bosch deep trench process enables high aspect ratio 
etching by the alternation of passivation and etching cycles. In 
each cycle a chemically inert polymer layer is uniformly 
deposited. This passivation layer prevents the sidewalls from 
being attacked in the subsequent etching step. By feeding high 
frequency plasma with etching gases, the passivation layer at 
the bottom of the trench is rapidly removed. After that, the 
silicon substrate is chemically etched. 
In the passivation and etching cycles of the Bosch process, 
the characteristic convexo-concave shape called scallop is 
naturally shaped. The scallop shape can be controlled by the 
etching process. Basically, a larger scallop is formed by the 
larger amount of silicon etching per 1 cycle with longer 
etching time. And the etching speed is comparatively high. For 
example, the process time is around 4 minutes per 40 μm deep 
trench with a sufficiently larger scallop (see Fig. 3). Therefore, 
the Bosch process is utilized to create the hole pocket rapidly. 
We made deep trenches of 5 μm, 10 μm, 20 μm and 40 μm 
line and space (L/S) on a trial basis. The difference in the level 
of the scallops was successfully shaped for all L/S deep 
trenches. The difference was about 0.5 μm regardless of the 
L/S size and continues in the back (see Fig. 4). The crystal 
defects in the sidewall are not observed by TEM analysis. 
Another process for thickening the SiO2 layer and electrode in 
the deep trench will be developed next. 
III. Performance	prediction	of	
novel	diode	by	TCAD	simulation	
The as-etched trench shape of the Bosch process was 
revealed by trial silicon etching in Chapter 2. The features of 
the trench shape are as follows (see Fig. 5). 
 The bottom shape has roundness. 
 The sidewall shape is a saw blade. 
 The pitch of the saw blade shape is about 2 μm. 
 The difference in the level of the saw blade shape is 
about 0.5 μm. 
 
 
Fig. 3. Cross-section SEM image of as-etched silicon substrate with 
scallop by Bosch deep trench process. 
 
 
Fig. 4. Sidewall AFM image of as-etched silicon substrate with 
continuous scallop in the back by the Bosch process deep trench. 
 
 
Fig. 5. Simulated novel diode structure with hole pockets. 
The performance of the novel diode with the characteristic 
trench shape is predicted by TCAD simulation. The novel 
diode has a higher doping concentration of the N- layer. The 
trench and the higher doping concentration equalize the 
electric field to maintain high blocking voltage in the off state 
and eventually the requisite thinner N-(base) layer thickness. 
The simulation results indicate a better trade-off curve of 
reverse recovery loss and chip size. Thanks to the waveform 
oscillation suppression with hole pockets, the diode with the 
thin N-base layer successfully reduces the reverse recovery 
loss to a half (see Fig. 6). Furthermore, the active chip size of 
the novel diode is reduced to two-thirds that of the 
conventional PiN diode at the certain forward voltage (see Fig. 
7). 
The surge voltage with noise is dramatically suppressed by 
the novel structure compared with the waveform of 
conventional punch-through structure and the simple deep 
trench diode without hole pockets (see Fig. 8). After reverse 
recovery, the stored carrier is swept out from the N-base layer. 
In this reverse recovery process, when the stored carrier is 
wsept out rapidly, the surge voltage and noise are generated 
intensely [16, 17]. The stored carrier of the novel diode 
successfully remained for a long time after reverse recovery 
because the hole pockets lose hole drift velocity (see Fig. 9 
and Fig. 10). 
Conventional and proposed applicable diode structures for 
the PiN diode are non punch-through, punch-through, 
superjunction, and lateral PiN diode with hole pockets [18] 
(see Fig. 11). In the three subjects of the reverse recovery loss 
and active chip size at a certain forward voltage, and surge 
voltage with noise during reverse recovery, no diode structure 
satisfies the three subjects. The novel vertical PiN diode 
structure with hole pockets is a strong candidate for when the 
simple fabrication process is established. 
The diode structure and fabrication process can be applied 
to all bipolar devices such as PiN diode and IGBT. 
 
IV. Conclusion	
The performance of the novel diode with the characteristic 
trench shape is predicted by TCAD simulation. A novel 600 V 
vertical PiN diode with hole pockets by the Bosch deep trench 
process was proposed for a better trade-off curve between 
reverse recovery loss and forward voltage. The reverse 
recovery loss is reduced to a half. In addition, the active chip 
size of the novel diode is reduced to two-thirds that of the 
conventional PiN diode. The novel diode structure is a strong 
candidate for when the simple fabrication process under 
development is established. The diode structure and 
fabrication process can be applied to all bipolar devices such 
as PiN diode and IGBT. 
Acknowledgment 
This study has been supported by the Adaptable and 
Seamless Technology Transfer Program through Target-driven 
R&D (A-STEP) of The Japan Science and Technology 
Agency (JST). We would like to thank Hironori Imaki for the 
TCAD simulation support. 
 
 
 
 
 
Fig. 6. Simulated trade-off curves between reverse recovery loss and 
forward voltage of novel vertical PiN diode and conventional diode 
without oscillation waveform. 
 
 
 
 
Fig. 7. Simulated trade-off curves between active chip size and forward 
voltage of novel vertical PiN diode and conventional diode without 
oscillation waveform. 
 
 
 
Fig. 8. Simulated reverse recovery waveform during reverse recovery 
(The thickness of all structures is 50 um). 
 
References 
[1] H. Ohashi, “Power divices now and future, strategy of Japan - Role of 
power electronics for a low carbon society,” Proc. of ISPSD, pp 9-12, 
2012. 
[2] R. Plikat, D. Silber, and W. Wondrak, “Very high voltage integration’ in 
SOI based on a new floating channel technology,” Proc. of IEEE 
International SOI Conference, pp. 59–60, 1998. 
[3] I. Omura, and A. Nakagawa, “Silicon on Inslator semiconductor device 
with increased withstand voltage,” United States Patent, 6049109, 2000. 
[4] H. Kapels, R. Plikat, and D. Silber, “Dielectric charge traps: a new 
structure element for power devices,” Proc. of ISPSD, pp. 205–208, 
2000. 
[5] X. Luo, B. Zhang, and Z. Li, “A novel E-SIMOX SOI high voltage 
device structure element for power devices,” Proc, ICCCAS 2005, 2005. 
[6] I. Omura, and A. Nakagawa, Japanese patent, No.3950105, 2007. 
[7] I. Omura, and A. Nakagawa, Japanese patent, No.3959125, 2007. 
[8] X. Luo, B. Zhang, Z. Li, Y. Guo, X. Tang, and Y. Liu, “A novel 700 V 
SOI LDMOS with double-sided trench,” IEEE Electron Dev Lett, pp. 
422-424, 2007. 
[9] X. Luo, B. Zhang, and Z. Li, “New high-voltage (>1200 V) MOSFET 
with the charge trenches on partial SOI,” IEEE Trans. on ED, Vol. 55, 
No. 7, pp. 1756–1761, 2008. 
[10] S. Shiraki, Y. Ashida, S. Takahashi, and N. Tokura, “Analysis of 
Transient Characteristics of Lateral IGBTs and Diodes on Silicon-on-
Insulator Substrates with Trenched Buried Oxide Structure,” Proc. of 
ISPSD, pp. 261–264, 2010. 
[11] X.M. Yang, B. Zhang, and XR. Luo, “Double Enhance Dielectric Layer 
Electric Field High Voltage SOI LDMOS,” Proc. of EDSSC, pp. 1–2, 
2011. 
[12] K. Kobayashi, T. Nishiguchi, S. Katoh, T.  Kawano, and Y. Kawaguchi, 
“100 V class multiple stepped oxide field plate trench MOSFET (MSO-
FP-MOSFET) aimed to ultimate structure realization,” ProcPeoc. of 
ISPSD, pp. 141-144, 2015. 
[13] M. Tsukuda, H. Imaki, and I. Omura, “Ultra-fast Lateral 600 V Silicon 
PiN Diode Superior to SiC-SBD,” Proc. of ISPSD, pp. 31–34, 2014. 
[14] M. Tsukuda, H. Imaki, and I. Omura, “Ultrafast lateral 600 V silicon 
SOI PiN diode with geometric traps for preventing waveform 
oscillation,” Solid-State Electronics, Vol. 104, pp. 61-69, 2015. 
[15] A. Baba, N. Uryu, and S. Sumi, “Fabrication of pn junction at the wall 
of deep trench for near-infrared sensor,” Digest of Papers MNC2011, 
26P-7-135, 2011. 
[16] M. Tsukuda, I. Omura, Y. Sakiyama, M. Yamaguchi, K. Matsushita, and 
T. Ogura, “Critical IGBT design regarding EMI and switching losses,” 
Proc. of ISPSD, pp. 185-188, 2008. 
[17] M. Tsukuda, Y. Sakiyama, H. Ninomiya, and M. Yamaguchi, “Dynamic 
punch-through design of high-voltage diode for suppression of 
waveform oscillation and switching loss,” Proc. of ISPSD, pp. 128-131, 
2009. 
[18] T. Fujihira, and Y. Miyasaka, “Simulated superior performances of 
semiconductor superjunction devices,” Proc. of ISPSD, pp. 423–426, 
1998. 
 
 
 
Fig. 9. Hole density during reverse recovery (The thickness of all structures is 50 um). 
 
 
 
Fig. 10. Hole drift velocity during reverse recovery.          Fig. 11. Conventional and applicable structures for high voltage diode with merit and drawback. 
Non punch-
through
Punch-
through
Deep trench with 
hole pockets
(Novel)
Reverse recovery loss
Surge voltage 
with noise 
Structure of 
vertical diode
Structure
Large
Small Large
Small
Superjunction
Small
Lateral and 
hole pockets
Small
Small
Small
Active chip size Small Small Large
Large
Small
P
N
N-
P
N
N-
P
N
N-P-
P
N
SiO2
SmallSmall
N-
SiO2
SiO2
P
N
N-


Novel 600 V Low Reverse Recovery Loss Vertical PiN Diode with Hole Pockets by Bosch Deep Trench

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Novel 600 V Low Reverse Recovery Loss Vertical PiN Diode with Hole Pockets by Bosch Deep Trench

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