Read the following passage and answer the questions that follow : Diffusion of impurity atoms in silicon is important in silicon integrated circuit processing. The idea of using diffusion techniques to alter the type of conductivity in silicon or germanium was disclosed in a patent by Pfann. Since then various ways of introducing dopants into silicon by diffusion have been studied with the goal of controlling dopant distribution, total dopant concentration, its uniformity reproducibility, and of processing a large number of device wafers in a batch to reduce the manufacturing cost. The diffusion is used to form bases, emitters and resistors in bipolar devices technology, to form source and drain regions and to dope polysilicon in MOS device technology. Dopant atoms that span a wide range of concentrations can be introduced into silicon in many ways.
The idea of using diffusion techniques was disclosed in patent by Pfann in the year :
1952
William Pfann disclosed the use of diffusion to alter the conductivity type of silicon and germanium in a patent of 1952 — option 2.
Where the date sits in the history of the technology, which is what makes it memorable rather than arbitrary:
| Year | Development |
|---|---|
| 1947 | Point-contact transistor demonstrated at Bell Labs |
| 1948 | Shockley's junction transistor conceived |
| 1952 | Pfann's diffusion patent |
| 1958 | First integrated circuit (Kilby) |
| 1960 | First planar MOSFET |
Pfann's own major contribution was zone refining, the technique of passing a molten zone repeatedly along an ingot so that impurities are swept to one end. It is what first made semiconductor-grade material pure enough to be useful, and it is the necessary complement to diffusion: one removes unwanted impurities, the other introduces wanted ones under control.
Why diffusion mattered so much. Before it, junctions were made by alloying or by grown-junction methods, in which the junction depth was poorly controlled and set by mechanical or crystal-growth conditions. Diffusion made the depth a function of temperature and time alone:
\(x_{j}\propto\sqrt{Dt}\)
— both quantities that a furnace controls precisely. Thin, reproducible base regions became possible, and with them high-frequency transistors; and because the process works on a whole wafer at once through an oxide mask, it is what made batch manufacture possible. The passage's phrase about "processing a large number of device wafers in a batch to reduce the manufacturing cost" points at exactly this.
The date's significance in one line : it falls between the invention of the transistor and the invention of the integrated circuit, and it is one of the steps that made the second possible.
Hence, the year is 1952.
Similar Questions
When silicon dioxide of thickness d is grown, the Silicon consumed is :
Match List - I with List - II.
List - I List - II (A) Annealing (I) Isolation (B) Sealing (II) Doping (C) Ion implantation (III) Packing density (D) Oxidation (IV) Crystal restoration Choose the correct answer from the options given below :
Arrange the following in ascending order based on their diffusivity :
(A) Boron
(B) Arsenic
(C) Antimony
(D) PhosphorusChoose the most appropriate answer from the options given below :
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The diffusivity determined experimentally over a range of diffusion temperatures can be expressed as :
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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 :
