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Using Laser And Volume Transmission Holographic Techniques For Abla Tion And/Or Laser Chemical Vapor Deposition Processing of Semicon Ductor Chips, Wafers And Substrates

IP.com Disclosure Number: IPCOM000120970D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 7 page(s) / 564K

Publishing Venue

IBM

Related People

LoDato, V: AUTHOR [+4]

Abstract

This article concerns employment of a thick volume transmission hologram to provide a high transmission optical system for energy intense ablation of polyimide-coated substrates/wafers. The disclosed holographic system will also be shown coupled with laser chemical deposition (LCVD) processes to solve problems encountered in the manufacture of chips and MLC (multilayer ceramic) devices, and in the mask repair procedures.

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Using Laser And Volume Transmission Holographic Techniques For Abla
Tion And/Or Laser Chemical Vapor Deposition Processing of Semicon
Ductor Chips, Wafers And Substrates

      This article concerns employment of a thick volume
transmission hologram to provide a high transmission optical system
for energy intense ablation of polyimide-coated substrates/wafers.
The disclosed holographic system will also be shown coupled with
laser chemical deposition (LCVD) processes to solve problems
encountered in the manufacture of chips and MLC (multilayer ceramic)
devices, and in the mask repair procedures.

      Laser ablation is a process whereby photons are absorbed via a
molecule such that a photodissociation occurs and particles of
molecules and/or polymers are released, i.e., causing desired
material removal with minimal thermal effect on surrounding areas.
The process of removing simultaneously a given pattern of material
requires a laser, a mask and an optical system.  To be meaningful to
the manufacturing environment, however, the ablation operation must
be performed within an allotted time.  The most important parameter
in this regard is a "non-lossy" mask that can cover a large surface
area.  A gating factor is the ratio of the transmission area to the
irradiating area. With conventional masking practice, assuming an
overall optical system efficiency of N90%, this area ratio acts to
limit the overall light transmission to N20%.

      The disclosed volume transmission holographic ablation process
overcomes the above limits by means of the system elements shown in
Fig. 1, in which the conventional metal or dielectic mask is replaced
by a thick volume transmission hologram.

      Identified in Fig. 1 are a laser 1, a beam shaper 2, a volume
transmission hologram 3, the target 4 and a polyimide coating 5, on
its surface.  The volume transmission hologram 3 can produce real
images on the target with a transmission efficiency of > 90%,
providing pattern ablation times in the order of 1/10 that possible
to obtain with a conventional mask utilizing tool.  Shown in Fig. 2
is a 200X photograph of a thick volume transmission hologram like
that identified in Fig. 1. It is capable of producing a matrix N 4.0
mil dots on 25.0 mil centers, each dot carrying all of the
information of the matrix pattern.  The feasibility of this concept
is demonstrated by the Fig. 3 photo which shows simultaneously
ablated holes in a coated wafer surface.  The hole quality can be
greatly improved over that shown by appropriate optical system
adjustment.  The target, a silicon wafer coated with polyimide, was
irradiated with an excimer laser and the pattern generated with a
thick volume transmission hologram.

      Numerous applications also exist in the semiconductor industry
in which transmission holography coupled with laser chemical vapor
deposition (LCVD) can be used to advantage, as when the laser
holographic deposition process is photolytic...