# US 12,111,569 B2 · Method for sizing a gray scale lithography mask

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- Number: US 12,111,569 B2
- Document ID: US12111569B2
- Status: Granted
- Kind: B2
- Application number: 18/601,853
- Filed: 2024-03-11
- Published: 2024-09-12
- Granted: 2024-10-08
- Earliest claimed: 2023-03-09
- Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Inventors: Ujwol Palanchoke
- Web page: https://patentgrep.com/patent/US12111569B2

## CPC

- G03F 1/70: Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging
- G03F 7/70283: {Mask effects on the imaging process}
- G03F 7/0005: {Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor}
- H10F 39/011: {Manufacture or treatment of image sensors covered by group H10F39/12}
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

A method for sizing a greyscale lithography mask is disclosed. The mask includes first opaque zones, being opaque to light-exposing radiation, located in first pixels forming a first mask grating. A first target density of a first surface density of first opaque zones is first established. This first target density makes it possible to expose a resin to light over a first given target thickness when it is exposed to the radiation through the first grating. The dimensions of the first pixels and the dimensions of the first opaque zones are then established, such that the value of an error over the first target thickness is less than a first given threshold. The dimensions obtained for the sizing of the first mask grating are used.

## Claims

### Claim 1

A method for sizing a greyscale lithography mask, the mask mainly extending along a horizontal plane defined by a first direction and a second direction, the plane being perpendicular to a main direction of a light-exposing radiation of a photosensitive resin through the mask, the mask comprising a plurality of opaque zones to the radiation, each opaque zone being located in a zone of the mask called pixel, the plurality of opaque zones comprising first opaque zones being located in first pixels, the first pixels forming a first grating of the mask, the method comprising the following steps:
establishing a first target density D100* of a first surface density D100 of first opaque zones within the first grating, the first target density D100* being configured to enable the resin to be exposed to light over a first given target thickness e1* when the resin is exposed to radiation through the first mask grating, the first target thickness e1* being measured in the main direction of the radiation,
obtaining a first value, for the first target density D100*, of the derivative with respect to the first surface density D100 of a first thickness e1 over which the photosensitive resin is exposed to light, when it is exposed to a radiation through the first grating having the first surface density D100, said first value being referenced
∂
e
1
(
D
100
*
)
∂
D
1
⁢
0
⁢
0
,
determining a first dimension Px,1 of the first pixels in the first direction, a first dimension Py,1 of the first pixels in the second direction, a first dimension Lx,1 of the first opaque zones in the first direction, a first dimension Ly,1 of the first opaque zones in the second direction, such that the value of an error over the first target thickness e1*, referenced MEEF(e1*), is less than
a first given threshold, MEEF(e1*) being calculated from the following formula:
MEEF
⁡
(
e
1
*
)
=
∂
e
1
(
D
100
⋆
)
∂
D
1
⁢
0
⁢
0
⁢
(
a
1
+
β
1
)
⁢
L
x
,
1
P
x
,
1
⁢
P
y
,
1
with
β
1
=
L
y
,
1
L
x
,
1
⁢
and
⁢
a
1
=
δ
⁢
L
y
,
1
δ
⁢
L
x
,
1
,
δ
⁢
L
x
,
1
being an error over Lx,1 and δLy,1 being an error over Ly,1,
using the dimensions obtained for the sizing of the first mask grating.

### Claim 2 (depends on 1)

The method according to claim 1, wherein a1 is between 0.8 and 1.2, preferably a is equal to 1.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the step of obtaining the first value of the derivative comprises the following steps:
providing a secondary resin of the same nature as the photosensitive resin,
exposing a plurality of regions of the secondary resin to light with a radiation, each region being exposed to light with a distinct dose of radiation,
for each region of the secondary resin, determining in the main direction of the radiation, a light-exposing thickness of the radiation in said region,
establishing, for each region of the secondary resin, a theoretical density of theoretical opaque zones on a theoretical mask, which, during exposure to a radiation of said region through the theoretical mask, would have made it possible to expose said region to the dose of radiation, to which said region is exposed,
establishing a model connecting the light-exposing thickness of the secondary resin layer to the opaque zone density from light-exposing thickness and theoretical density data obtained for each of the regions.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the step of establishing, for each region of the secondary resin, of the theoretical density of theoretical opaque zones, is done at least by application of the following formula:
D
i
=
1
-
Q
i
Q
max
with i indexing the different regions of the secondary resin, Di the theoretical density associated with the region i, Qi the dose of radiation to which the region i is exposed and Qmax=max(Qi).

### Claim 5 (depends on 1)

The method according to claim 1, wherein the step of obtaining the first value of the derivative comprises the following steps:
providing a test mask having a plurality of test gratings, each having a distinct density of test opaque zones,
providing a test resin of the same nature as the photosensitive resin,
exposing a plurality of regions of the test resin to light with a radiation through the test mask, the exposing to light of each region being done through a distinct test grating,
determining, for each region of the test resin, a light-exposing thickness of the radiation in said region,
establishing a model connecting the light-exposing thickness of the test resin layer to the density of test opaque zones from light-exposing thickness data obtained for each of the regions.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the first dimension Px,1 of the first pixels in the first direction and the first dimension Py,1 of the first pixels in the second direction are each less than a main wavelength of the radiation.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the first pixels have a square shape in the horizontal plane and wherein Px,1=Py,1=P.

### Claim 8 (depends on 7)

The method according to claim 7, wherein the first opaque zones have a square shape in the horizontal plane and wherein Lx,1=Ly,1=L.

### Claim 9 (depends on 7)

The method according to claim 7, wherein:
the first opaque zones have a square shape in the horizontal plane and wherein Lx,1=Ly,1=L, and
MEEF
⁡
(
e
1
*
)
=
∂
e
1
(
D
100
⋆
)
∂
D
1
⁢
0
⁢
0
⁢
2
⁢
D
100
⋆
P
.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the plurality of opaque zones comprises at least second opaque zones being located in second pixels, the second pixels forming a second mask grating, the method further comprising the following steps:
establishing a second target density D200* of a second surface density D200 of second opaque zones within the second grating, the second target density D200* being configured to enable the resin to be exposed to light over a second given target thickness e2* when the resin is exposed to the radiation through the second mask grating, the second target thickness e2* being measured in the main direction of the radiation, the second target thickness e2* being distinct from the first target thickness e1*,
obtaining a second value, for the second target density D200*, of the derivative with respect to the second surface density D200 of a second thickness e2 over which the photosensitive resin is exposed to light when it is exposed to a radiation through the second grating having the second surface density D200, referenced
∂
e
2
(
D
200
⋆
)
∂
D
2
⁢
0
⁢
0
,
determining a second dimension Px,2 of the second pixels in the first direction, a second dimension Py,2 of the second pixels in the second direction, a second dimension Lx,2 of the second opaque zones in the first direction, a second dimension Ly,2 of the second opaque zones in the second direction, such that the value of an error over the second target thickness e2*, referenced MEEF(e2*) is less than a second given threshold, MEEF(e2*) being calculated from the following formula:
MEEF
⁡
(
e
2
*
)
=
∂
e
2
(
D
200
⋆
)
∂
D
2
⁢
0
⁢
0
⁢
(
a
2
+
β
2
)
⁢
L
x
,
2
P
x
,
2
⁢
P
y
,
2
.
β
2
=
L
y
,
2
L
x
,
2
⁢
and
⁢
a
2
=
δ
⁢
L
y
,
2
δ
⁢
L
x
,
2
,
δ
⁢
L
x
,
2
with
being an error over Lx,2 and δLy,2 being an error over Ly,2,
using the dimensions obtained for the sizing of the second mask grating.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the second grating forms, in the horizontal plane, a closed contour, wherein the first grating is located.

### Claim 12 (depends on 11)

The method according to claim 11, wherein the closed contour formed by the second grating is substantially circular.

### Claim 13 (depends on 11)

The method according to claim 11, wherein the second threshold for the error over the second target thickness e2* is less than the first threshold for the error over the first target thickness e1*.

### Claim 14 (depends on 1)

The method for manufacturing a greyscale lithography mask comprising the following steps:
sizing the mask by implementation of the method according to claim 1,
manufacturing the mask thus sized.