Direct access logic testing in integrated circuits

Details Direct access logic testing in integrated circuits Direct access logic testing in integrated circuits

1999-03-30

2002-05-07

Decady, Albert (Department: 2133)

Error detection/correction and fault detection/recovery

Pulse or data error handling

Digital logic testing

C365S201000

Reexamination Certificate

active

06385748

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of integrated circuit testing.
2. Description of the Related Art
An integrated circuit (IC) is a miniature electric circuit containing large numbers of discrete electronic circuit elements, such as transistors, resistors, capacitors, and diodes, which are packaged as a single unit with leads extending from it for input, output, and power-supply connections. The electronic circuit elements are formed by selective manipulation of a single chip of semiconductor material, often in combination with various other semi-conducting and/or conducting materials.
It is common in the art to roughly classify integrated circuits dependent upon their transistor density. Presently, there are effectively four common integrated circuit classifications: small-scale integrated circuits (SSIs); medium-scale integrated circuits (MSIs); large-scale integrated circuits (LSIs); and very-large-scale integrated circuit (VLSIs). Exactly what transistor densities constitute the various “classes” varies, but at present SSIs typically include up to several tens of transistors, MSIs include from many tens to several hundred transistors; LSIs include from several hundred to a few thousand transistors; and VLSIs several hundred thousand or more. Most ICs in use today would constitute VLSIs.
One powerful feature of integrated circuits is the ability to use such integrated circuits to produce several levels of abstraction, which is useful for complete design. For example, integrated circuit design can be viewed at one level of abstraction in terms of discrete electronic circuit components (e.g., resistors, capacitors, inductors, transistors, diodes, etc.). Integrated circuit design can also be viewed at a next-higher layer of abstraction in terms of logic diagrams consisting of well-defined digital boolean logic circuits such as AND, NAND, OR, and NOR gates, where each such gate consists of well-defined congeries of the discrete electronic circuit elements. Integrated circuit design can also be viewed at yet a next-higher layer of abstraction known as Register Transfer Level (RTL), which consists of program-like statements describing the movement or processing of data between storage elements. Integrated circuits can also be viewed at a yet again higher layer of abstraction known as a functional block diagram layer, which shows the major subcomponents of a design. This is the level at which the highest conceptual design work is done.
Typically, IC design is done at the functional block diagram, RTL, and logic diagram levels. It is common for whole teams of people (and sometimes whole companies) to focus on various aspects of the design at various abstraction levels. However, as noted, the design process rarely proceeds at a lower level than that of logic diagrams. Below this level, it is common to program the desired logic diagram layouts into artificially intelligent software, which automatically produces discrete circuit component level diagrams to be enacted within the integrated circuit.
A particular type of IC is known as an Application Specific Integrated Circuit (ASIC). An ASIC is an integrated circuit that is designed and built to perform a particular set of functions via the use of an integrated circuit. One example of a way in which ASICs are commonly used is provide hardware implementations of computer software application programs. That is, use of ASICs allows system designers to work at and design at a software layer of abstraction in order to produce and debug a computer software application program to perform a desired function. Thereafter, the higher-level software layer of abstraction level of design can be translated to hardware level design via the use of various techniques well-known in the art, such as the Very High Speed Integrated Circuit Hardware Description Language (VHDL). The hardware level design can then be implemented in an IC, and since the IC will be designed to implement a particular application program, it has become common in the art to refer to such ICs as “Application Specific” ICs, or ASICs.
Those skilled in the art will recognize that ASICs do not operate in a vacuum. That is, it is common, even in environments where ASICS are utilized, for the ASICs to interface and/or utilize one or more standard data processing system components, such as additional processing devices (e.g., one or more central processing units (CPUs), or dedicated graphics processors), communications channels (e.g., Peripheral Component Interface (PCI), or Advanced Graphics Processing (AGP) data buses).
In the past, the presence of ASICs in an environment typically meant that an independent, freestanding, IC existed for each ASIC present in addition to any other more standard integrated circuits necessary to support the system. However, efforts are now being made within the industry to move toward System-On-a-Chip (SOC) designs wherein any desired ASICs are actually designed into, and made part of, ICs which have one or more pre-existing “cores” which provide the IC with logic sufficient to provide one or more standard functions, such as the functions of one or more standard data processing system components. It is common in the art to refer to non-core logic, such as an ASIC, as user-defined logic (UDL). An example of such a SOC is shown in FIG.
1
.
With reference to
FIG. 1
, shown is a partial functional block diagram level related art integrated circuit SOC
100
. As shown, contained within SOC
100
are CPU core
102
, on-chip processor bus
104
, on-chip bridge
106
, system memory
107
, on-chip peripheral component internal (PCI) bus
108
, and peripheral bus components
110
-
114
, and ASIC
116
(an example of UDL).
SOC
100
is a functional block diagram representation of various functional blocks performing their various functions. As referenced above, the actual implementation of the various functional blocks within any IC containing SOC
100
will be via the use of perhaps several hundred thousand interconnected discrete circuit level components.
As noted above, the discrete circuit level components are produced via the selective manipulation of a single piece of semiconductor material, where such selective manipulation usually includes the use of other semi-conducting and/or conducting materials. The discrete circuit level components are created via this selective manipulation.
The regions affected by the selective manipulation of the single piece of semiconductor material are almost unimaginably small. For example, current VLSI production procedures produce the discrete circuit components by manipulating material by use of sub-micron width (i.e., widths of less that (1/1,000,000) of a meter) lines drawn, or “etched,” in the semiconductor material. Furthermore, the sizes of the regions manipulated decrease virtually every week.
Due to the very small regions manipulated during VLSI production, errors invariably occur. This can be the result of contamination of the material, or minor variations in the length, width, or height of lines etched. These errors in production often result in errors in the behavior of the discrete electronic circuit level components.
As noted, the higher abstraction logic diagram level is designed using logic diagram level component circuits consisting of congeries of discrete circuit level components. Consequently, errors in production sufficient to produce errors in the behavior of the discrete circuit level components can “propagate” upwards to the logic diagram level since the logic diagram circuits are built from congeries of these malfunctioning circuit components. If the errors are severe, then such malfunctioning will be very apparent in that the affected logic diagram level circuits will not function. However, if the malfunction is not severe, it is possible that the affected logic diagram level components will perform, but will perform in such a way that is out of design tolerances, which can cause a general system malfunction or failure as these logic diagram level

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