Match List - I with List - II. Choose the correct answer from the options given below :List - I List - II (A) Annealing (I) Isolation (B) Sealing (II) Doping (C) Ion implantation (III) Packing density (D) Oxidation (IV) Crystal restoration
(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
Two of the pairings are the heart of the question, and they are consecutive steps of the same process: ion implantation dopes, and annealing repairs the damage it causes. The code is (A)-(IV), (B)-(III), (C)-(II), (D)-(I) — option 4.
(C) Ion implantation and doping. Dopant ions are accelerated to tens or hundreds of keV and fired into the wafer. Compared with thermal diffusion it offers precise control of the dose, since the implanted charge is simply the integrated beam current, and of the depth, set by the accelerating energy. It is also anisotropic, so the dopant goes where the mask allows and not sideways.
(A) Annealing and crystal restoration — and why the two steps belong together. An implanted ion arrives with enormous energy and knocks silicon atoms off their lattice sites as it comes to rest, leaving a badly damaged and sometimes amorphous layer. Worse, the implanted atoms sit wherever they stopped, mostly in interstitial positions where they contribute no carriers at all. Annealing at 900–1000 °C does two things at once: it restores the crystal order, and it moves the dopants onto substitutional lattice sites so that they become electrically active. Without it, an implant would leave the wafer damaged and undoped in effect.
(D) Oxidation and isolation. A grown SiO2 layer has a band gap of about 9 eV and is an excellent insulator, so a thick field oxide grown between devices — the LOCOS process — keeps neighbouring transistors from interacting. Oxide also serves as the gate dielectric and as a diffusion mask, but among the four options offered, isolation is its match.
(B) Sealing and packing density. This is the pairing left by elimination, and it makes sense in terms of the final passivation and encapsulation of the die: how compactly devices and their interconnect can be sealed together governs how many fit in a given area.
| Step | Purpose |
|---|---|
| Ion implantation | Introduce dopants precisely |
| Annealing | Repair lattice, activate dopants |
| Oxidation | Insulate and isolate |
| Sealing | Protect the finished die |
Hence, the correct code is (A)-(IV), (B)-(III), (C)-(II), (D)-(I).
Similar Questions
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Important Questions from Semiconductor Process Flow
A. For impurity diffusion in semiconductor, concentration gradient is the only essential requirement.
B. Annealing is a mandatory step after ion-implantation.
C. Wet etching is normally anisotropic
D. High temperature is required for the growth of $SiO_2$ because oxidation reaction takes place at high temperature
E. Bird's beak formation is a characteristic of LOCOS isolation
Choose the correct answer from the options given below:
Arrange the given process steps in sequence for self-aligned gate formation.
A. Thermal oxidation to grow gate oxide.
B. Polysilicon deposition
C. Photolithography using gate mask
D. Etching of polysilicon and oxide
E. Source/drain diffusion
Choose the correct answer from the options given below:
- Match the LIST-I with LIST-IIChoose the correct answer from the options given below:
LIST-I LIST-II A. Shallow trench isolation (STI) I. Low static power dissipation B. Junction isolation II. High static power dissipation C. CMOS technology III. High component density D. Bipolar IC technology IV. Low component density Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Impurity diffusion in semiconductor essentially needs very high temperature.
Reason R: Diffusivity of impurity atoms is negligibly small at room temperature.
In the light of the above statements, choose the most appropriate answer from the options given below
- In particle beam lithography, the resolution depends upon :
