CN102117012A - Method for increasing focal depth in lithography process - Google Patents
Method for increasing focal depth in lithography process Download PDFInfo
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- CN102117012A CN102117012A CN2009102476365A CN200910247636A CN102117012A CN 102117012 A CN102117012 A CN 102117012A CN 2009102476365 A CN2009102476365 A CN 2009102476365A CN 200910247636 A CN200910247636 A CN 200910247636A CN 102117012 A CN102117012 A CN 102117012A
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Abstract
The invention provides a method for increasing the focal depth in lithography process, which comprises the following steps: firstly exposing a photoresist to obtain dense lines, then performing a second exposure with a specially-produced mask pattern to remove other unnecessary lines and leave isolated lines, wherein the focal depth of the obtained isolated lines is identical to that of the dense lines. With the method, the focal depth of the lines can be increased, and much workload of optical proximity effect correction technology OPC is saved.
Description
Technical field
The present invention relates to field of semiconductor manufacture, particularly a kind of method of optical semiconductor carving technology.
Background technology
In field of semiconductor manufacture, photoetching process is crucial technological process at present.Along with dwindling that technology node continues, the trend that some special pattern exposure depths of focus diminish is more rapid, makes the exposure difficulty of litho machine increase, and lithographic process window diminishes, and keeps very difficulty of photoetching process stability.
Along with the raising of semiconductor devices integrated level, the requirement of projection optical system resolution is improved constantly.Have some resolution enhance technology (RET) to be used for increasing depth of focus at present, mainly contain four kinds, a kind of is on lighting system, as adopting off-axis illumination; A kind of is the phase place of modulation photo etched mask, as adopting phase-shift mask (PSM) technology; A kind of is to add auxiliary pattern near mask pattern, proofreaies and correct (OPC) technology as adding optical approach effects such as serif, scattering strip.Also having a kind of is to adopt the immersion lithography technology, promptly is full of the depth of focus that a kind of high refractive index liquid medium can improve projection optical system between last optical surface of projection optical system and image planes.
Along with technology node to when 32 nanometers even 22 nanometers, because the limiting resolution of existing immersion 193nm litho machine can only reach 45 nanometer nodes (as the 1700i of ASML company series litho machine), realize more minor node (as 32 nanometers even 22 nanometers) photoetching, using double-pattern technology (Double Patterning) is exactly highly effective real means.So far, the double-pattern technology has just formally been climbed up the arena of history, and it is bringing into play increasing effect aspect raising resolution and the depth of focus.
Intensive lines are more much bigger than the depth of focus of isolated lines in photoetching process, generally are to use auxiliary line (Assist Feature) and improve the method that isolates the lines depth of focus at present.Robertson is (Peter Robertson in his Master's thesis, ProximityEffects in Projection Lithography:A Case Study of the Perkin-Elmer " Micralign. " M.S.Thesis, U.C.Berkeley (Berkeley, California, 1981)) suggestion: increase auxiliary hachure on the isolated line next door, their can reduce the approach effect of isolated line in the not imaging of when exposure.This conclusion is published in the nineteen eighty-two SPIE photoetching meeting.
Also have certain limitation but use auxiliary line,, must use bigger exposure energy, will inevitably increase the workload of OPC like this because will make not imaging on photoresist of auxiliary line; The depth of focus that has added the isolated lines of auxiliary line in addition still is smaller than the depth of focus of intensive lines.
Summary of the invention
The depth of focus that the objective of the invention is in order to make isolated lines is the same with intensive lines big, reduces the workload of OPC simultaneously, adopts double-exposure technique to obtain the isolated lines of big depth of focus on intensive lines.
A kind of method that improves depth of focus in the photoetching process of the present invention comprises the steps:
1) two kinds of mask patterns of design have intensive lines and isolated lines respectively;
2) linging (HMDS), the hydrophobicity of increase silicon chip surface is removed surface moisture;
3) resist coating obtains required film thickness and inhomogeneity photoresist layer;
4) solvent in the photoresist is removed in soft baking, and discharges the stress in the photoresist, increases the thermal stability of photoresist;
5) mask pattern with intensive lines carries out the exposure first time on photoresist, exposes intensive lines;
6) mask pattern with isolated lines carries out the exposure second time, removes unwanted other the intensive lines of designing institute, only stays the desired isolated lines of design;
7) effect of light acid catalysis is quickened in postexposure bake (PEB), reduces standing wave effect;
8) develop, make the light acid and developer solution reaction that exposure, PEB obtain to obtain needed isolated line figure;
9) back baking, the thermal stability of increase photoresist increases photoresist and resists etched ability.
The center of a certain lines in the intensive lines that expose for the first time must be aimed in the center of isolated lines when wherein, exposing for the second time.
Wherein, the width of isolated lines should smaller or equal to the width of the line thickness of intensive lines and two spacings with, greater than the live width of intensive lines.
Use photoetching technological method of the present invention, can improve the depth of focus of isolated lines, make and isolate lines depth of focus and intensive lines basically identical, save the auxiliary pattern design, the workload of saving OPC simultaneously.
Description of drawings
Fig. 1 is a photoetching technological method process flow diagram of the present invention;
Fig. 2 is the intensive lines mask pattern of the present invention;
Fig. 3 is the isolated lines mask pattern of the present invention.
Embodiment
Below, describe in detail according to a preferred embodiment of the invention in conjunction with the accompanying drawings.
A kind of method that improves depth of focus in the photoetching process of the present invention, technological process comprises the steps: as shown in Figure 1
1) two kinds of figures of design on a mask are respectively intensive lines and isolated lines;
2) linging (HMDS), the hydrophobicity of increase silicon chip surface is removed surface moisture;
3) resist coating TOK P3232 obtains required film thickness (5000A) and the homogeneity (photoresist layer of Range＜50A);
4) solvent in the photoresist is removed in soft baking (110C60S), and discharges the stress in the photoresist, increases the thermal stability of photoresist;
5) on photoresist, carry out the exposure first time with intensive bargraphs district, expose intensive lines according to common process;
6) on photoresist, carry out the exposure second time with isolated lines graph area, remove unwanted other the intensive lines of designing institute, only stay the desired isolated lines of design;
7) (PEB 110C60S), quickens the effect of light acid catalysis, reduces standing wave effect in postexposure bake;
8) develop, make the light acid and developer solution reaction that exposure, PEB obtain to obtain needed isolated line figure;
9) back baking, the thermal stability of increase photoresist increases photoresist and resists etched ability.
Intensive lines that the present invention uses and isolated lines graphic designs are as shown in Figures 2 and 3.It is the intensive lines of 150/150nm that intensive bargraphs adopts LINE/SPACE, and it is the isolated bargraphs of 430nm that isolated bargraphs adopts live width.Suppose that intensive lines live width is L, isolated lines live width is M, article two, the spacing between the intensive lines is S, alignment precision is A, L＜M＜=2S+L then, consider alignment precision, then can more accurately be expressed as L+2A＜M＜=2S+L-2A, concrete isolated lines live width with alignment precision and finally on silicon chip required line thickness be relevant.During concrete exposure, exposure for the second time must make expose for the first time center of a certain lines in the intensive lines of the centrally aligned that isolates lines, feasible lines that only stay this aligning.Alignment precision is the smaller the better, if with two masks, then need to guarantee the mask alignment precision.Alignment so in the experiment is that two kinds of figures are made on the mask at present, and such alignment precision can reach about 2nm.
The result of exposure:
With 150nm+/-15 is critical size (CD) specification, and then the depth of focus DOF of the intensive lines of single exposure is 0.5um; Exposure latitude EL＞10%;
And the DOF of double exposure also is 0.5um; EL＞10%.
Above presentation of results double exposure can make the DOF of isolated lines and the DOF basically identical of intensive lines.
Described in this instructions is several preferred embodiment of the present invention, and above embodiment is only in order to illustrate technical scheme of the present invention but not limitation of the present invention.All those skilled in the art all should be within the scope of the present invention under this invention's idea by the available technical scheme of logical analysis, reasoning, or a limited experiment.
Claims (3)
1. a method that improves depth of focus in the photoetching process comprises the steps:
1) two kinds of mask patterns of design have intensive lines and isolated lines respectively;
2) linging (HMDS), the hydrophobicity of increase silicon chip surface is removed surface moisture;
3) resist coating obtains required film thickness and inhomogeneity photoresist layer;
4) solvent in the photoresist is removed in soft baking, and discharges the stress in the photoresist, increases the thermal stability of photoresist;
5) mask pattern with intensive lines carries out the exposure first time on photoresist, exposes intensive lines;
6) mask pattern with isolated lines carries out the exposure second time, removes unwanted other the intensive lines of designing institute, only stays the desired isolated lines of design;
7) effect of light acid catalysis is quickened in postexposure bake (PEB), reduces standing wave effect;
8) develop, make the light acid and developer solution reaction that exposure, PEB obtain to obtain needed isolated line figure;
9) back baking, the thermal stability of increase photoresist increases photoresist and resists etched ability.
2. method according to claim 1, the centrally aligned of the isolated lines center of a certain lines in the intensive lines of exposing for the first time when it is characterized in that exposing for the second time.
3. method according to claim 1, it is characterized in that isolated lines width should smaller or equal to the width of the line thickness of intensive lines and two spacings with, greater than the live width of intensive lines.
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| CN2009102476365A CN102117012A (en) | 2009-12-30 | 2009-12-30 | Method for increasing focal depth in lithography process |
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| CN2009102476365A CN102117012A (en) | 2009-12-30 | 2009-12-30 | Method for increasing focal depth in lithography process |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102445835A (en) * | 2011-10-12 | 2012-05-09 | 上海华力微电子有限公司 | Optical proximity correction modeling method of SRAM source and drain dimension |
| CN102446712A (en) * | 2011-09-08 | 2012-05-09 | 上海华力微电子有限公司 | Method for increasing double patterning process windows |
| CN102445834A (en) * | 2011-09-15 | 2012-05-09 | 上海华力微电子有限公司 | Optical modeling proximity correction method of SRAM (Static Random Access Memory) grid dimension |
| CN112987487A (en) * | 2021-02-22 | 2021-06-18 | 上海华力集成电路制造有限公司 | OPC correction method for graph structure with different graph density ends |
-
2009
- 2009-12-30 CN CN2009102476365A patent/CN102117012A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102446712A (en) * | 2011-09-08 | 2012-05-09 | 上海华力微电子有限公司 | Method for increasing double patterning process windows |
| CN102446712B (en) * | 2011-09-08 | 2013-12-04 | 上海华力微电子有限公司 | Method for increasing double patterning process windows |
| CN102445834A (en) * | 2011-09-15 | 2012-05-09 | 上海华力微电子有限公司 | Optical modeling proximity correction method of SRAM (Static Random Access Memory) grid dimension |
| CN102445835A (en) * | 2011-10-12 | 2012-05-09 | 上海华力微电子有限公司 | Optical proximity correction modeling method of SRAM source and drain dimension |
| CN112987487A (en) * | 2021-02-22 | 2021-06-18 | 上海华力集成电路制造有限公司 | OPC correction method for graph structure with different graph density ends |
| CN112987487B (en) * | 2021-02-22 | 2024-03-08 | 上海华力集成电路制造有限公司 | OPC correction method for graph structure with different graph density ends |
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Application publication date: 20110706 |