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Determination of Process Specifications from Product Specifications

IP.com Disclosure Number: IPCOM000118617D
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Kurtzberg, JM: AUTHOR [+2]

Abstract

Today, there is no systematic way for determining the appropriate specifications for manufacturing processes, based on Product Requirements. This disclosure presents a recursive technique for automatic determination of the specifications of all manufacturing processes leading to an acceptable product.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 48% of the total text.

Determination of Process Specifications from Product Specifications

      Today, there is no systematic way for determining the
appropriate specifications for manufacturing processes, based on
Product Requirements.  This disclosure presents a recursive technique
for automatic determination of the specifications of all
manufacturing processes leading to an acceptable product.

      Let a manufacturing process consist of a sequence of processes,
each of which may be a simple or a compound process.  Let the product
resulting from these processes have a functionally acceptable
performance window.  Problem to be solved is the identification of
the setpoints and tolerances of all process steps, which result in a
product within its functional specifications window.  This window may
consist of one or more functional requirements which must be
satisfied simultaneously.  If multiple solutions exist, it is
desirable to select  the one which is the least restrictive on the
fabrication process. Since  a complex manufacturing process may
involve thousands of variables, it  is also required that as few as
possible variables be analyzed at any one, time.  This requirement is
a practical one, and its aim is to insure  manageability and
computability of complicated manufacturing processes.

      As an illustration of the problem, consider the manufacturing
of a simple planar CMOS capacitor.  The manufacturing process may
consist of thermal oxidation of doped silicon wafers, followed by an
implant step, a drive-in (anneal) step, and final metallization.  It
is required  that the capacitor threshold voltage be within a
specific range and its  transconductance at a particular gate voltage
be within a certain range.  The problem is the determination of the
ranges of the various times, temperatures, energies, and dosages,
etc. (i.e., tolerances for  all independent variables), which result
in product capacitors which meet  the above requirements.  If
possible, it is desirable to select the solution which permits the
widest fluctuations in the incoming doped silicon wafers.

The following procedure will achieve the above goal:

STEP 1
  Partition the manufacturing process into a hierarchical cluster
structure.  This means that a process supplies to any subsequent
process only those variables relevant to it.  In this manner, process
responses at one level become input variables at following levels.
The result is  a hierarchical structure in which a relative small
number of variables  are needed to describe any level.  The final,
top level describes the product in terms of input variables, which
are output (response) variables of lower levels.  The result of this
step is a flowchart of the  manufacturing process in which each of
the manufacturing steps is clearly  defined in terms of its inputs
and outputs.  This includes the final step whose output is the
product with its functional parameters. Now,  one can use
manufacturing...