Piezoelectric Effect Basics
A piezoelectric substance is one that produces an electric charge when a mechanical stress is applied (the substance is
squeezed or stretched). Conversely, a mechanical deformation (the substance shrinks or expands) is produced when an
electric field is applied. This effect is formed in crystals that have no center of symmetry. To explain this, we have to look at
the individual molecules that make up the crystal. Each molecule has a polarization, one end is more negatively charged
and the other end is positively charged, and is called a dipole. This is a result of the atoms that make up the molecule and
the way the molecules are shaped. The polar axis is an imaginary line that runs through the center of both charges on the
molecule. In a monocrystal the polar axes of all of the dipoles lie in one direction. The crystal is said to be symmetrical
because if you were to cut the crystal at any point, the resultant polar axes of the two pieces would lie in the same direction
as the original. In a polycrystal, there are different regions within the material that have a different polar axis. It is asymmetrical
because there is no point at which the crystal could be cut that would leave the two remaining pieces with the
same resultant polar axis. In order to produce the piezoelectric effect, the polycrystal is heated under the application of a strong electric field. The
heat allows the molecules to move more freely and the electric field forces all of the dipoles in the crystal to line up and face
in nearly the same direction The piezoelectric effect can now be observed in the crystal. Figure 3 illustrates the piezoelectric effect. Figure 3a shows
the piezoelectric material without a stress or charge. If the material is compressed, then a voltage of the same polarity as
the poling voltage will appear between the electrodes (b). If stretched, a voltage of opposite polarity will appear (c). Conversely,
if a voltage is applied the material will deform. A voltage with the opposite polarity as the poling voltage will cause
the material to expand, (d), and a voltage with the same polarity will cause the material to compress (e). If an AC signal is applied then the material will vibrate at the same frequency as the signal (f).
Using the Piezoelectric Effect
The piezoelectric crystal bends in different ways at different frequencies. This bending is called the vibration mode. The
crystal can be made into various shapes to achieve different vibration modes. To realize small, cost effective, and high performance
products, several modes have been developed to operate over several frequency ranges. These modes allow us
to make products working in the low kHz range up to the MHz range. Figure 4 shows the vibration modes and the frequencies
over which they can work.
An important group of piezoelectric materials are ceramics. Murata utilizes these various vibration modes and ceramics to
make many useful products, such as ceramic resonators, ceramic bandpass filters, ceramic discriminators, ceramic traps,
SAW filters, and buzzers.
Jika ingin jalan-jalan dengan biaya transportasi yang sangat murah ke Jepang sebaiknya pilihlah pada saat liburan anak-anak sekolah di Jepang. Periode liburan anak-anak sekolah di Jepang dilaksanakan 3 kali dalam satu tahun yaitu pada 1 Maret ~ 10 April, 20 Juli ~ 10 September, dan 10 Desember ~ 10 Januari. Adapun periode penjualan tiket ini dilaksanakan pada tanggal 20 Febuari ~ 31 Maret, 1 Juli ~ 31 Agustus, dan 1 Desember ~ 31 Desember.
Selama musim liburan ini dijual tiket bebas naik KA (Japan Railways) diseluruh Jepang, kalau boleh meminjam istilah di kuliner ya kita dapat menyebut “all you can eat” (apa hubungannya yah?? 🙂 ). Biaya yang perlu dikeluarkan dalam satu hari naik KA (JR) ke seluruh kota di Jepang cukup 2300 yen. Tiket ini biasa disebut dengan nama Seishun Juhachi kippu atau tiket anak muda 18 tahun. Tiket ini dijual per 5 kali pemakaian seharga 11.500 yen artinya tiket ini dapat digunakan oleh 5 orang yang berbeda secara bersamaan dalam 1 (satu) hari atau digunakan oleh 1 (satu) orang yang sama selama 5 hari tidak perlu berturut-turut.
Greek alphabet
Αα : Alpha
Νν : Nu
Ββ : Beta
Ξξ : Xi
Γγ : Gamma
Οο : Omicron
Δδ : Delta
Ππ : Pi
Εε : Epsilon Ρρ : Rho
Ζζ : Zeta
Σσς : Sigma
Ηη : Eta
Ττ : Tau
Θθ : Theta
Υυ : Upsilon
Ιι : Iota
Φφ : Phi
Κκ : Kappa
Χχ : Chi
Λλ : Lambda
Ψψ : Psi
Μμ : Mu
Ωω : Omega
Photolithography is the process of transferring geometric shapes on a mask to the surface of a silicon wafer. The steps involved in the photolithographic process are wafer cleaning; barrier layer formation; photoresist application; soft baking; mask alignment; exposure and development; and hard-baking.
Wafer Cleaning, Barrier Formation and Photoresist Application
In the first step, the wafers are chemically cleaned to remove particulate matter on the surface as well as any traces of organic, ionic, and metallic impurities. After cleaning, silicon dioxide, which serves as a barrier layer, is deposited on the surface of the wafer. After the formation of the SiO2 layer, photoresist is applied to the surface of the wafer. High-speed centrifugal whirling of silicon wafers is the standard method for applying photoresist coatings in IC manufacturing. This technique, known as “Spin Coating,” produces a thin uniform layer of photoresist on the wafer surface.
Positive and Negative Photoresist
There are two types of photoresist: positive and negative. For positive resists, the resist is exposed with UV light wherever the underlying material is to be removed. In these resists, exposure to the UV light changes the chemical structure of the resist so that it becomes more soluble in the developer. The exposed resist is then washed away by the developer solution, leaving windows of the bare underlying material. In other words, “whatever shows, goes.” The mask, therefore, contains an exact copy of the pattern which is to remain on the wafer.
Negative resists behave in just the opposite manner. Exposure to the UV light causes the negative resist to become polymerized, and more difficult to dissolve. Therefore, the negative resist remains on the surface wherever it is exposed, and the developer solution removes only the unexposed portions. Masks used for negative photoresists, therefore, contain the inverse (or photographic “negative”) of the pattern to be transferred. The figure below shows the pattern differences generated from the use of positive and negative resist.
Negative resists were popular in the early history of integrated circuit processing, but positive resist gradually became more widely used since they offer better process controllability for small geometry features. Positive resists are now the dominant type of resist used in VLSI fabrication processes.
Soft-Baking
Soft-baking is the step during which almost all of the solvents are removed from the photoresist coating. Soft-baking plays a very critical role in photo-imaging. The photoresist coatings become photosensitive, or imageable, only after softbaking. Oversoft-baking will degrade the photosensitivity of resists by either reducing the developer solubility or actually destroying a portion of the sensitizer. Undersoft-baking will prevent light from reaching the sensitizer. Positive resists are incompletely exposed if considerable solvent remains in the coating. This undersoft-baked positive resists is then readily attacked by the developer in both exposed and unexposed areas, causing less etching resistance.
Mask Alignment and Exposure
One of the most important steps in the photolithography process is mask alignment. A mask or “photomask” is a square glass plate with a patterned emulsion of metal film on one side. The mask is aligned with the wafer, so that the pattern can be transferred onto the wafer surface. Each mask after the first one must be aligned to the previous pattern.
Once the mask has been accurately aligned with the pattern on the wafer’s surface, the photoresist is exposed through the pattern on the mask with a high intensity ultraviolet light. There are three primary exposure methods: contact, proximity, and projection. They are shown in the figure below.
Contact Printing
In contact printing, the resist-coated silicon wafer is brought into physical contact with the glass photomask. The wafer is held on a vacuum chuck, and the whole assembly rises until the wafer and mask contact each other. The photoresist is exposed with UV light while the wafer is in contact position with the mask. Because of the contact between the resist and mask, very high resolution is possible in contact printing (e.g. 1-micron features in 0.5 microns of positive resist). The problem with contact printing is that debris, trapped between the resist and the mask, can damage the mask and cause defects in the pattern.
Proximity Printing
The proximity exposure method is similar to contact printing except that a small gap, 10 to 25 microns wide, is maintained between the wafer and the mask during exposure. This gap minimizes (but may not eliminate) mask damage. Approximately 2- to 4-micron resolution is possible with proximity printing.
Projection Printing
Projection printing, avoids mask damage entirely. An image of the patterns on the mask is projected onto the resist-coated wafer, which is many centimeters away. In order to achieve high resolution, only a small portion of the mask is imaged. This small image field is scanned or stepped over the surface of the wafer. Projection printers that step the mask image over the wafer surface are called step-and-repeat systems. Step-and-repeat projection printers are capable of approximately 1-micron resolution.
Development
One of the last steps in the photolithographic process is development. The figure below shows response curves for negative and positive resist after exposure and development.
At low-exposure energies, the negative resist remains completely soluble in the developer solution. As the exposure is increased above a threshold energy Et, more of the resist film remains after development. At exposures two or three times the threshold energy, very little of the resist film is dissolved. For positive resists, the resist solubility in its developer is finite even at zero-exposure energy. The solubility gradually increases until, at some threshold, it becomes completely soluble. These curves are affected by all the resist processing variables: initial resist thickness, prebake conditions, developer chemistry, developing time, and others.
Hard-Baking
Hard-baking is the final step in the photolithographic process. This step is necessary in order to harden the photoresist and improve adhesion of the photoresist to the wafer surface.
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Doa Kemuliaan kepada Bapa,
Eikou wa chichi to ko to seirei ni
Hajime no youni imamo itSumo yoyoni. Amen
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Doa Salam Maria,
Megumi aFureru sei maria,
Shu wa anata to tomo ni oraremasu.
Shu wa anata wo erabi, shukuFuku sHi,
Anata no ko iesu mo shukuFuku saremasHita.
Kami no haha sei maria,
Tsumi bukai watashitachi no tameni
Ima mo sHi wo mukaeru toki mo inotte kudasai. Amen.
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Doa Bapa Kami,
Ten ni orareru watashitachi no chichi yo,
Mina ga sei to saremasu youni
Mikuni ga kimasu youni.
Mikokoro ga ten ni okonawareru toori
chi ni mo okonawaremasu you ni.
Watashitachi no hogoto no kate wo
kyou mo oatae kudasai.
Watashitachi no tsumi wo oyurushi kudasai.
Watashitachi mo hito wo yurushimasu.
watashitachi wo yuuwaku ni ochiirasezu,
aku kara osukui kudasai.
Tanda Salib,
Chichi to ko to seirei no mina ni yotte, Amen.
Saya menabrak seorang yang tidak dikenal ketika ia lewat. “Oh, maafkan saya”
adalah reaksi saya. Ia berkata, “Maafkan saya juga. Saya tidak melihat
Anda.” Orang tidak dikenal itu, juga saya, berlaku sangat sopan. Akhirnya
kami berpisah dan mengucapkan selamat tinggal.
Namun cerita lainnya terjadi di rumah, lihat bagaimana kita memperlakukan
orang-orang yang kita kasihi, tua dan muda. Pada hari itu juga, saat saya
tengah memasak makan malam, anak lelaki saya berdiri diam-diam di samping
saya. Ketika saya berbalik, hampir saja saya membuatnya jatuh. “Minggir,”
kata saya dengan marah. Ia pergi, mungkin hati kecilnya hancur. Saya tidak
menyadari betapa kasarnya kata-kata saya kepadanya.
Ketika saya berbaring di tempat tidur, dengan halus Tuhan berbicara padaku,
“Sewaktu kamu berurusan dengan orang yang tidak kau kenal, etika kesopanan
kamu gunakan, tetapi anak-anak yang engkau kasihi, sepertinya engkau
perlakukan dengan sewenang-wenang. Coba lihat ke lantai dapur, engkau akan
menemukan beberapa kuntum bunga dekat pintu. Bunga-bunga tersebut telah
dipetik sendiri oleh anakmu; merah muda, kuning dan biru. Anakmu berdiri
tanpa suara supaya tidak menggagalkan kejutan yang akan ia buat bagimu, dan
kamu bahkan tidak melihat matanya yang basah saat itu.”
Seketika aku merasa malu, dan sekarang air mataku mulai menetes. Saya
pelan-pelan pergi ke kamar anakku dan berlutut di dekat tempat tidurnya,
“Bangun, nak, bangun,” kataku. “Apakah bunga-bunga ini engkau petik
untukku?” Ia tersenyum, ” Aku menemukannya jatuh dari pohon. ”
“Aku mengambil bunga-bunga ini karena mereka cantik seperti Ibu.Aku tahu Ibu
akan menyukainya, terutama yang berwarna biru.” Aku berkata, “Anakku, Ibu
sangat menyesal karena telah kasar padamu. Ibu seharusnya tidak membentakmu
seperti tadi.”
Si kecilku berkata, “Oh, Ibu, tidak apa-apa. Aku tetap mencintaimu.” Aku pun
membalas, “Anakku, aku mencintaimu juga, dan aku benar-benar menyukai
bunga-bunga ini, apalagi yang biru.” Apakah anda menyadari bahwa jika kita
mati besok, perusahaan dimana kita bekerja sekarang bisa saja dengan
mudahnya mencari pengganti kita dalam hitungan hari? Tetapi keluarga yang
kita tinggalkan akan merasakan kehilangan selama sisa hidup mereka.
Mari kita renungkan, kita melibatkan diri lebih dalam kepada pekerjaan kita
ketimbang keluarga kita sendiri, suatu investasi yang tentunya kurang
bijaksana, bukan? Jadi apakah anda telah memahami apa tujuan cerita di atas?
Apakah anda tahu apa arti kata FAMILY?
Dalam bahasa Inggris, FAMILY = KELUARGA
FAMILY = (F)ATHER (A)ND (M)OTHER (I) (L)OVE (Y)OU
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