Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
1995-11-22
2002-03-12
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S005000, C430S321000, C716S030000, C716S030000
Reexamination Certificate
active
06355387
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for making a mask pattern, and more particularly to a method for making a mask pattern by correcting the size of a hole diameter of a mask for forming a contact hole.
2. Description of the Background Art
Making of a contact hole is indispensable in fabrication of LSI, and low precision of the hole diameter of a contact hole (hereinafter called contact hole diameter) leads to a contact failure previously control of the contact hole diameter has been attempted by correcting the mask pattern for forming a contact hole.
FIG. 24
is a flowchart showing a conventional technique of correcting the hole diameter of a mask (hereinafter called mask hole diameter) for forming a contact hole.
First, while making a mask pattern by using CAD, a check card is prepared. A check card is a collection of process flow for fabricating an LSI, specifying when to use which mask, when to make or remove which layer, etc.
Conventionally, by trial fabrication of LSI using a designed mask, the section of the LSI was observed by a microscope, and the actual contact hole diameter was measured. When the contact hole diameter was larger than a desired value, the mask hole diameter was designed smaller, and when the contact hole diameter was smaller than a desired value, the mask hole diameter was designed larger, and thus the mask pattern was corrected by such feedback.
For example, using a mask hole diameter designed to fabricate a contact hole diameter of 0.5 &mgr;m, if the actually fabricated contact hole diameter is 0.4 &mgr;m, the mask hole diameter is designed so as to fabricate a contact hole diameter of 0.6 &mgr;m. Or, if the fabricated contact hole diameter is 0.6 &mgr;m, the mask hole diameter is designed so as to fabricate a contact hole diameter of 0.4 &mgr;m.
It is, however, not practical to execute this step for all contact holes. In the LSI, there are hundreds of thousands of contact holes on one chip.
In such circumstances, it is also attempted to loosen the design rule of the LSI. The contact hole diameter depends not only on the mask hole diameter, but also on the undulations of the region for forming the contact hole, and therefore when the undulations of the region are moderate, the precision of the contact hole diameter is enhanced. Accordingly, for example, if forming of lithographic pattern is possible at 0.5 &mgr;m, then by designing the LSI by the 1 &mgr;m rule, undulations in the region for forming the contact hole are set to moderate, and hence the precision of the contact hole diameter may be enhanced. It, however, requires a wide area for realizing the LSI, and the transmission characteristic of the element deteriorates.
SUMMARY OF THE INVENTION
A first aspect of the invention relates to a method of making a mask pattern, by correcting a mask pattern used for providing an actual pattern in a processing region of an object, comprising steps of (a) making the mask pattern, (b) judging undulations of the object, (c) predicting dimensions of the actual pattern depending on the degree of the undulations, and (d) correcting by giving a correction amount to the dimensions of the mask pattern, depending on the result of the step (c).
A second aspect of the invention relates to a method of making a mask pattern of the first aspect, wherein the actual pattern is provided by forming a resist on the object, and shaping the resist depending on the mask pattern, and the step (c) includes steps of (c-1) determining the film thickness increment or decrement of the resist in the processing region, on the basis of the film thickness of the resist when the object is flat, and (c-2) predicting, on the basis of the film thickness increment or decrement, that the direction of deviation of the dimensions of the actual pattern when the processing region is concave as compared with the actual pattern when the processing region is flat, and the direction of the dimensions of the actual pattern when the processing region is convex as compared with the actual pattern when the processing region is flat are reverse to each other, and that the dimensions of the actual pattern are deviated larger when the degree of undulations of the processing region is greater as compared with when the processing region is flat.
A third aspect of the invention relates to a method of making a mask pattern of the second aspect, wherein a surface shape of the object is recognized as a surface height, relative to a foundation region expanding at least in a first direction and a second direction reverse to the first direction, and the step (b) includes steps of (b-1) determining the surface height by simulation, (b-2) specifying the position of the processing region in the foundation region, (b-3) setting a first region expanding in the first direction from the processing region, and a second region expanding in the second direction from the processing region, (b-4) detecting whether a first state of the surface height tending to increase relative to the first direction or a second state tending to decrease relative to the first direction is present, in both the first and second regions, on the basis of the result of the step (b-1), and (b-5) judging undulations about the first and second directions in the processing region on the basis of the result of the step (b-4).
A fourth aspect of the invention relates to a method of making a mask pattern of the third aspect, wherein the step (b-4), respectively in the first and second regions, has steps of (b-4-1) determining a position for taking the maximum value of the surface height, (b-4-2) determining a position for taking the minimum value of the surface height, (b-4-3) determining a shape height by subtracting the surface height of the processing region from the maximum value, (b-4-4) determining a shape depth by subtracting the minimum value from the surface height of the processing region, (b-4-5) judging a presence of the first state when the shape height is greater than the shape depth, and (b-4-6) judging a presence of the second state when the shape height is smaller than the shape depth.
A fifth aspect of the invention relates to a method of making a mask pattern of the fourth aspect, wherein the step (b-4-5) comprises, when the shape height is greater than the shape depth, a step of (b-4-5-1) taking the shape height as a first value, the step (b-4-6) comprises, when the shape height is smaller than the shape depth, a step of (b-4-6-1) taking the value multiplying the shape depth by (−1) as the first value, the step (c-1) has steps of (c-1-1) obtaining an altitude amount at an intermediate value of the first value of the first region and the first value of the second region, and (c-1-2) determining the film thickness increment or decrement on the basis of the altitude amount, and the absolute value of the film thickness increment or decrement is greater when the absolute value of the altitude amount is greater, and the sign of the altitude amount and the sign of the film thickness increment or decrement are different from each other, in the step (c-1-2).
A sixth aspect of the invention relates to a method of making a mask pattern of the fifth aspect, wherein the step (c-1-1) comprises a step of (c-1-1-1) obtaining an slope amount at an intermediate value of the value of dividing the first value in the first region by the second value in the first region, and the value of dividing the first value in the second region by the second value in the second region, and the film thickness increment or decrement is determined also on the basis of the slope amount in the step (c-1-2), and the absolute value of the film thickness increment or decrement is greater when the absolute value of the slope amount is greater.
A seventh aspect of the invention relates to a method of making a mask pattern of the fourth aspect, wherein the step (b-4-5) comprises, when the shape height is greater than the shape depth, steps of (b-4-5-1) taking the shape height as a first value, and (b-4-5-2) taking
Fujinaga Masato
Soeda Shinya
Angebranndt Martin
Mitsubishi Denki & Kabushiki Kaisha
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