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Sains Malaysiana 42(5)(2013): 643–648
Formation of Porous Silicon: Mechanism of Macropores
Formation
in n-Type Si
(Pembentukan Silikon Berliang: Mekanisme Pembentukan Liang Makro
dalam Si Jenis-n)
Nurul Izni Rusli, Mastura Shafinaz Zainal
Abidin, Budi Astuti & Nihad K. Ali
Faculty
of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
Abdul Manaf Hashim*
Malaysia-Japan International Institute
of Technology (MJIIT)
Universiti Teknologi Malaysia
International Campus, Jalan Semarak 54100 Kuala Lumpur
Malaysia
Received:
7 January 2012/Accepted: 21 May 2012
ABSTRACT
We report the formation of macropores in n-Si (100) substrates for
different etching times of 20, 40 and 60 min at a constant current density of
25 mA/cm2 under front-side illumination in HF:ethanol (1:4) solution. After etching for 20 min, four-branch-shaped pores of various
sizes were observed at discrete locations. Etching time of 40 min led to the
formation of highly connected four-branch-shaped pores as the branches of
adjacent pores appeared to connect to each other. As the etching time was
increased further to 60 min, the density of interconnected branches increased
remarkably. The macropore formation process occurred in three consecutive
phases. The current burst model was used to discuss this process. Formation of
four-branch-shaped pores at random locations were observed because current
bursts are more likely to nucleate where other current bursts took place
initially.
Keywords: Electrochemical etching; etching time; illumination;
porous silicon
ABSTRAK
Kami melaporkan pembentukan liang makro dalam substrat Si(100)
jenis-n untuk masa punaran yang berbeza iaitu 20, 40 dan 60 min pada ketumpatan
arus malar sebanyak 25 mA/cm2 di bawah pencahayaan arah
depan dalam larutan HF:etanol (1:4). Selepas punaran selama 20 min,
liang-liang bercabang-empat pelbagai saiz dapat diperhatikan pada lokasi
tertentu. Masa punaran 40 min menyebabkan pembentukan liang-liang
bercabang-empat yang bersambungan kerana cabang pada liang-liang bersebelahan
telah muncul untuk menyambung antara satu sama lain.
Apabila masa punaran dilanjutkan kepada 60 min, ketumpatan cabang-cabang yang
saling bersambungan meningkat dengan ketara. Pembentukan liang makro ini berlaku dalam tiga fasa berturut-turut. Model limpahaan arus telah
digunakan untuk membincangkan proses ini. Pembentukan liang-liang bercabang-empat pada lokasi rawak telah diperhatikan kerana limpahan arus lebih
cenderung untuk terbentuk pada tempat limpahan arus yang telah berlaku
sebelumnya.
Kata kunci: Masa punaran; pencahayaan; punaran
elektrokimia; silikon berliang
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*Corresponding
author; email: manaf@fke.utm.my
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