09-06-2010, 01:14 PM
vlsi.docx (Size: 1.47 MB / Downloads: 396)
Presented By:
D.Sairam(05631A0433)
D.Satishvarma(05631A0437)
ISTE Membership numbers: 1782 &1786
SRI VB4KATESHWARA ENGINEERING COLLEGE
SURYAPET-508 213. NALGONDA DIST.(A.P)
Accredited by NBA
Abstract:
Since the invention of the integrated circuit in 19S8,the number of processing steps required to make one has grown from Less than 10 to several hundreds. At the same time-, the silicon wafers on which the VLSI ICs. are produced have gone from being coin sized to being dinner-plate sized. Today one of these 300-mm wafers can yield more than 700 Ics. With such a large number of les coming from a single wafer and with wafers coming off manufacturing lines at rates of tens or thousands a month* companies can quickly find themselves suffering from 1oosses especially in turbulent markets .Batch process which is being followed nowadays by VLSI chip makers is one of the main reasons for these losses. In batch process machines work on a large batch of wafers at the same time and take more than three months to produce VLSI I cs. To avoid the over production of chips ,one method is to go for single wafer process. In single wafer process semiconductor companies will be able to produce chips more quickly when the orders came in in the exact quantities specified by those orders. In this paper the IC- fabrication steps are given in brief. Batch process and the Single wafer process are compared in detai1. In the following years all manufacturers will inevitably adopt single Wafer manufacturing process in order to have fast and cheaper , smaller and good quality chips.
Why Design Integrated Circuits?
Integrated Circuit (IC) technology is the enabling technology for a whole host of innovative devices and systems that have changed the way we live. Integrated circuits are much smaller and consume less power than the discrete components used to build electronic systems before the 1960s. Integration allows us to build systems with many more transistors, allowing much more computing power to be applied to solving a problem. Integrated circuits are also much easier to design and manufacture and are more reliable than discrete systems; that makes it possible to develop special-purpose systems that are more efficient than general “ purpose computers for the task at hand.
Components of Chip:-
An Integrated Circuit (IC) is a combination of interconnected circuit elements inseparably associated on or within a continuous substrate.
The substrate
is the supporting material upon or within which an IC is fabricated or to which an IC is attached.
A monolithic IC is an IC whose elements are formed in place upon or within a semiconductor substrate with at lease one of the elements formed within the substrate.
A hybrid IC consists of a combination of two or more IC types or an IC with some discrete elements.
A wafer (or slice)
is the basic physical unit used in processing. It generally contains a large number of identical ICs, Typically, the wafer is circular; production wafers have a diameter of 4,5 or 6 in. The chip is one of the repeated ICs on a wafer. A typical production wafer may contain as few as 20 or 30 ICs or as many as several hundred or even several thousand, depending upon the complexity and size of the circuit being fabricated. The terms die and bar are used interchangeably for chip in some companies.
A test plug, or process control bar (PCB),
or process control monitor (PCM), is a special chip that is repeated only a few times on each wafer. It is used to monitor the process parameters of the technology. After processing, the validity of the process is verified by measuring, at the wafer probe level, the characteristics of devices and / or circuits on the test plug.
If the measurements of key parameters at the test plug level are not acceptable, the wafer is discarded. Front end construction of components
A test cell, or test lead,
is a special chip repeated only a few times on each wafer. It differs from the test plug in that the circuit designer includes this cell specifically to monitor the performance of elementary sub circuits or subcomponents.