Mesoscopic defect detection for reticle inspection

Patent metadata

Field	Value
Publication number	US-9607371-B2
Application number	US-201414227782-A
Country	US
Kind code	B2
Filing date	Mar 27, 2014
Priority date	Apr 1, 2013
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

In some embodiments, a method and/or system may include detecting defects in photomasks. The method may include acquiring a first image of a first die. The method may include acquiring a second image of a second die. In some embodiments, the method may include dividing the first and the second image into a number of first and second portions respectively. The method may include reducing one or more differences in sizing of the first and the second portions. In some embodiments, the method may include determining a difference in a function derived from an image intensity between the corresponding first and second portions. The method may include summing the differences in the function between the corresponding first and second portions. The method may include detecting mesoscopic scale defects in the second die.

First claim

What is claimed is:

1. A method of detecting defects in photomasks, comprising:
acquiring a first image of a first die;
acquiring a second image of a second die;
dividing the first and the second image into a number of first and second portions respectively;
reducing one or more differences in sizing of the first and the second portions comprising determining b|∇I(x,y)|, wherein b is linearly proportional to a critical dimension sizing difference;
determining differences in a function derived from an image intensity between the corresponding first and second portions;
summing the differences in the function between the corresponding first and second portions;
and
detecting mesoscopic scale defects in the second die.

2. The method of claim 1 , wherein the first image and/or the second image is acquired using transmitted light and/or reflected light.

3. The method of claim 1 , further comprising generating a graphical display map of the differences as a function of the locations associated with the first die and the second die.

4. The method of claim 1 , wherein the first die comprises a reference die.

5. The method of claim 1 , wherein the second die comprises a test die.

6. The method of claim 1 , wherein b is derived from minimizing the following objective function:

∑

x
,
y

⁢

⁢

[

I
test

⁡

(

x
,
y

)

-

I
ref

⁡

(

x
,
y

)

-

b
⁢



▽
⁢

⁢

I
ref

⁡

(

x
,
,
y

)



]

2

.

7. The method of claim 1 , wherein when b varies within a first and/or a second portion of the first and second images the first and/or the second portion is subdivided into subportions.

8. The method of claim 6 , further comprising mapping defects in the second die upon deriving b.

9. The method of claim 1 , wherein the first die comprises a theoretically modelled die.

10. The method of claim 9 , further comprising calibrating the theoretically modelled die, comprising:
deriving a set of modeling parameters (b; {right arrow over (α)}) wherein b denotes the bias amount on features and {right arrow over (α)} denotes a set of modeling parameters; and
freezing {right arrow over (α)} and floating b, for each patch image, by minimizing

∑

x
,
y

⁢

⁢

[

I
test

⁡

(

x
,
y

)

-

I
ref

⁡

(

x
,

y
;
b

)

❘

]

2

.

11. A system, comprising:
a processor;
a memory medium coupled to the processor that stores program instructions executable by the processor to:
acquire a first image of a first die;
acquire a second image of a second die;
divide the first and the second image into a number of first and second portions respectively;
reduce one or more differences in sizing of the first and the second portions comprising determining b|∇I(x,y)|, wherein b is linearly proportional to a critical dimension sizing difference;
determine differences in a function derived from an image intensity between the corresponding first and second portions;
sum the differences in the function between the corresponding first and second portions; and
detect mesoscopic scale defects in the second die.

12. The system of claim 11 , wherein the program instructions are further executable by the processor to generate a graphical display map of the differences as a function of the locations associated with the first die and the second die.

13. The system of claim 11 , wherein the first die comprises a reference die.

14. The system of claim 11 , wherein the second die comprises a test die.

15. The system of claim 11 , wherein b is derived from minimizing the following objective

Assignees

• Shi Rui-Fang
• Guo Zhian
• Li Bing
• Kla Tencor Corp

Inventors

• Shi Rui-Fang
• Guo Zhian
• Li Bing

Classifications

• G06K2209/19

  Physics · mapped topic

• G06T7/001 Primary

  using an image reference approach · CPC title

• G06K9/4642

  Physics · mapped topic

• G06V2201/06

  Recognition of objects for industrial automation · CPC title

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title