Radiation imagery chemistry: process – composition – or product th – Using reflected radiation – e.g. – reflex copying – etc.
Reexamination Certificate
1998-10-31
2001-10-30
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Using reflected radiation, e.g., reflex copying, etc.
C430S321000, C430S324000, C430S005000, C438S697000, C216S038000
Reexamination Certificate
active
06309809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to image recording processes and more particularly to employing self-correcting processes of forming images in connection with photolithography of multiple images aligned to each other or a like process akin to printing onto a previously imaged substrate.
2. Description of Related Art
FIGS. 1-3
show a perfect process flow, in the prior art, for manufacture of a device
10
. The intent here is to sequentially produce two images leading to formation of two openings in semiconductor layers. Typically a spatial relationship between the edges of two openings in overlaying imaging levels is to be reproduced to tight manufacturing tolerances.
Referring to
FIG. 1
, in the practice of prior art a device
10
is formed on a semiconductor substrate
11
, which is shown with a photoresist etch mask
12
formed thereon with an opening
6
therethrough which was used to form a hollow opening B with sidewalls
7
in the substrate
11
by anisotropic etching.
Referring to
FIG. 2
, the device
10
of
FIG. 1
is shown after the mask
12
has been removed from substrate
11
and a film
13
, e.g. an oxide layer, has been formed by any method desired (that narrows down the width of opening B) to form a narrower opening
6
′ with sidewalls
16
centered on opening B. This image modification is achieved strictly by process means. As a result, this derivative image defined by sidewalls
16
of opening
6
′ is self-aligned to the opening B with sidewalls
7
and it maintains the same center as opening B, as well as replicating the shape of B in an inward direction while retaining excellent centerline level-to-level overlay component of edge-to-edge overlay. Then a new blanket photoresist layer
14
has been formed on the device
10
covering dielectric film
13
.
Then a new photolithographic image of opening
9
in an optical mask (or reticle)
8
is formed by exposing photo-resist layer
14
of FIG.
2
and developed into a well opening
15
in photoresist mask
14
′ as seen in FIG.
3
. The photo-resist layer
14
of
FIG. 2
has been formed into a photoresist etch mask
14
′ of
FIG. 3
with the pattern for an opening
15
above the opening B. The photoresist etch mask
14
′ is used to etch opening E (with sidewalls
18
) in the film
13
and, possibly, substrate
11
(as illustrated in FIG.
3
). Level-to-level, edge-to-edge overlay in the plane of the top surface of the substrate
11
of the opening
15
(in resist etch mask layer
14
′) with the opening B limited by sidewalls
7
or with its derivative defined by sidewalls
16
is critical.
In order to maintain tight production control of this edge-to-edge overlay, dimensions of features in both masking levels and level-to-level centerline overlay must be simultaneously controlled.
FIG. 3
illustrates perfect overlay of the openings E and B in the substrate
11
, as desired in an ideal result.
FIG. 4
shows a typical problem with practicing the prior art approach of
FIGS. 1-3
. Specifically the centerline level-to-level overlay error is illustrated, where, at the time of exposure, the opening
9
in mask
8
is misplaced to the left from its intended position. The result is formation of opening
15
′ in photoresist layer
14
′, also misplaced to the left, and a subsequent etching of opening
18
′ (E) into the substrate
11
with encroachment on the left sidewall
16
of well B formed by film
13
. In other words, because of misalignment of opening
9
in mask
8
with opening B in substrate
11
, its image defined by sidewalls
15
′ in the photoresist
141
has been produced too far to the left. An error of making the width of opening
9
in mask
8
or of its image
15
′ in the photoresist
14
′ too large would lead to a similar problem.
When tight tolerances of level-to-level centerline overlay and linewidth (critical dimension, CD) for both openings B and E are not maintained, opening E may be defined outside of the region bounded by sidewalls
16
″ of film
13
within opening B, resulting in a device malfunction.
Making an opening E is a new patterning step which, in the present state of the art, does not take account of the existing (previously patterned on substrate) pattern B. At the most, measures are taken to suppress influence of the prior pattern on the new pattern formed, as in antireflection coatings, dyed photoresist, multilayer photoresist systems, surface imaging, etc., which are all expensive enhancements for the problem of opening (image) E size definition or tolerancing, each detrimentally affected by the existence of prior pattern B.
Using all of the above art does not overcome the underlying problem of proper image size and centerline overlay control, concurrently, in many imaging layers (which leads to device malfunction.) While these approaches mitigate the problem, they do it in an unsatisfactory way, because of the unacceptable levels of complexity and expense. The existing imperfections in masks(reticles) and printing machines (image distortion) and image size variation in the prior layer containing opening B and the new imaging layer (containing opening E) are not even addressed. The prior art is based upon the philosophy of control of all tolerances individually (for definition of typical current practices of prior art see Booth et al., “A Statistical Approach to Quality Control of Non-normal Lithographic Overlay Distortion”, IBM J. Res. Develop., Vol. 36, pp. 835-844; 1992).
Maintaining the required lithographic tolerances is a difficult task which requires ever increasing complexity of microlithographic masks and printers, processes, metrology, etc. and, hence, is becoming economically unjustifiable. For a current account of overlay difficulties, see Yanof et al. “Overlay Measurement and Analysis of X-ray/Optical Lithography for Mix-and-Match Device Applications” SPIE Proc. 2194, pp. 36-50 (1994) page 50 in the “Conclusions”, where it is stated that the overlay errors in optical to X-ray matching are as large as 60-70 nm from x-ray mask distortion alone, with distortion of optical mask and printer being comparable in magnitude (and additive in the practice of the prior art).
Edge-to-edge overlay (separation) of opening E with reference to opening B is critically dependent on centerline level-to level overlay (O/L) and on tolerances of linewidth (critical dimension, CD) for both openings B and E. In the prior art, a tight control of CD for both the openings B and E, as well as O/L of the opening E upon the opening B are individually maintained as is demanded by the market place, and accordingly, there is no alternative to that approach. The unacceptable alternatives are relaxed device ground rules which would result in non-competitive (slow, much energy consumption) or use of processes unable to support the required dimensional control and resulting in manufacture of unreliable devices.
SUMMARY OF THE INVENTION
An object of this invention is to employ any physical characteristics of a previously patterned feature to better form a new pattern in the course of an imaging process and associated image recording process.
The practitioner of this new art is invited to utilize the simplest imaging techniques which are inexpensive and easy to control to tight tolerances, as opposed to those techniques that are both complex and difficult to control, to achieve a desired result. The practitioner uses a larger number of steps which are individually simpler to execute. As a reward for patience, diligence, adaptation to the laws of nature, the user can achieve results that are otherwise impossible, while using existing technology. As the nearest analog to what is being proposed, lithography of the school of artist Suzuki Harunobu (Japan, 1725-1770) is cited, where up to ten levels of aligned (color) lithography have been inexpensively executed to mass-produce Ukiyo-e (mirror of the floating world) woodblock prints, using the fullest technology of the day.
In accordance
Goodman Douglas Seymore
Starikov Alexander
Angebranndt Martin
International Business Machines - Corporation
Jones II Graham S.
Schnurmann H. Daniel
LandOfFree
Multi-layer integrated imaging/image recording process with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer integrated imaging/image recording process with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer integrated imaging/image recording process with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2609831