CN100383932C - Silicon wet-etching technology - Google Patents
Silicon wet-etching technology Download PDFInfo
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- CN100383932C CN100383932C CNB2005100190524A CN200510019052A CN100383932C CN 100383932 C CN100383932 C CN 100383932C CN B2005100190524 A CNB2005100190524 A CN B2005100190524A CN 200510019052 A CN200510019052 A CN 200510019052A CN 100383932 C CN100383932 C CN 100383932C
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- mask
- etching
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- wet
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Abstract
The present invention discloses a silicon wet-etching technology. The present invention comprises following steps: (1) a Cr mask with the thickness of 50 to 600 nm is sputtered on a clean silicon wafer; (2) a pattern is prepared on the Cr mask with the utilization of photoetching technology; (3) the layer of the Cr mask is etched in (NH4) 2 Ce (NO3) 5 solution with the component proportion that every 100 ml of the etching solution is composed of 5 to 20 grams of cerium nitrate, 1.5 to 8 ml of perchloric acid and water as the rest part of the liquid; (4) wet etching is carried out to the etched silicon wafer with the utilization of KOH solution; (5) the layer of the Cr mask on the silicon wafer is removed by the etching solution of (NH4) 2 Ce (NO3) 5. Because the combination between the Cr and the silicon material, enough fastness can be ensured in wet etching, and the selectivity of the Cr mask in the KOH etching solution. The present invention has the characteristics of little toxicity and easy processing.
Description
Technical field
The invention belongs to the etch mask technology, be specifically related to a kind of silicon wet-etching technology.
Background technology
The core process of wet etching is a selective etch, promptly utilizes mask and the substrate characteristics that etch rate differs greatly in etching liquid, obtains the figure that needs in substrate.Therefore, the making of mask is the important process link that realizes wet method.
More common mask material is SiO in the wet etching of silicon at present
2(silicon dioxide) and Si
3N
4(silicon nitride), what use is concentrated base and etching liquid is general, as KOH etc.Use SiO
2(silicon dioxide) and Si
3N
4(silicon nitride) exists some problems as etch mask, makes that the effect of etching is not fine.Therefore, be necessary to seek a kind of new mask material, and make corresponding scheme.
SiO
2The film mask is not fine to the selectivity of KOH etching liquid, the SiO of general heat growth
2Ratio with the etch rate of silicon in 50 ℃ KOH solution is approximately 1: 100, and the SiO that the heat growth forms
2Film is various SiO
2Best in the film to the KOH corrosion stability.Therefore, SiO
2Mask can only be used for the silicon wet etching of shallow-layer; And to SiO
2Processing use the bigger HF of toxicity (hydrofluoric acid) usually, environment and human body are all had certain danger.
Si
3N
4The etch rate of mask in KOH is minimum, so its selectivity is fine.But Si
3N
4Differ bigger with the thermal coefficient of expansion of silicon, its film crackle can occur on silicon chip, even comes off, and can not play the effect of mask at all.Therefore, must adopt with SiO
2Layer is an intermediary layer, earlier growth one deck SiO on silicon wafer
2, and then low temperature depositing Si
3N
4, could guarantee Si
3N
4Mask is solid and reliable in etching liquid.And, Si
3N
4Wet etching method very complicated, generally can only use RIE (reactive ion etching), the technology more complicated is to the equipment requirements height.
Summary of the invention
The objective of the invention is to overcome the deficiencies in the prior art part, a kind of silicon wet-etching technology is provided, it is little that this technology has toxicity, the processing characteristic of simple.
A kind of silicon wet-etching technology provided by the invention, its step comprises:
(1), on the silicon chip of cleaning sputter Cr mask, the Cr mask thicknesses is 50nm～600nm;
(2), on the Cr mask, utilize photoetching process to prepare the photoresist figure;
(3), at (NH
4)
2Ce (NO
3)
5In the solution Cr mask is carried out etching, (NH
4)
2Ce (NO
3)
5The composition proportion of solution is: in the etching liquid of every 100ml, ammonium ceric nitrate is: 5 grams～20 grams, and perchloric acid is: 1.5 milliliters～8 milliliters, surplus is a water;
(4), use the silicon chip after KOH solution is etched to the Cr mask to carry out wet etching;
(5), use (NH
4)
2Ce (NO
3)
5Etching liquid is removed the Cr mask on the silicon chip.
The present invention uses Metal Cr to do mask material, particularly, has following technique effect:
(1), Cr combines closely with silicon materials, is usually used in the intermediate layer of other metal materials of deposition on silicon base, therefore can guarantee enough fastnesses when wet etching.
(2) chemical property of Cr is stable, and is good to the repellence of highly basic, reaction hardly in the KOH etching liquid, so the selectivity of Cr mask in the KOH etching liquid is very good.
(3), Cr is at (NH
4)
2Ce (NO
3)
5Can dissolve rapidly in (ammonium ceric nitrate) solution, simultaneously (NH
4)
2Ce (NO
3)
5Solution can not etch silicon, and nontoxic substantially, environmental sound.Therefore can utilize (NH
4)
2Ce (NO
3)
5The Cr mask is carried out figure processing.
(4), can utilize standard photolithography techniques with the masterplate figure transfer to the Cr mask, technology is simple, and equipment is not had special requirement.
The comparing result of the present invention and prior art is as follows:
The various mask material characteristic contrasts of table 1
| Mask material | SiO 2 | Si 3N 4 | Cr |
| Typical case's preparation method | Thermal oxidation | CVD | Sputter |
| The typical process mode | The HF wet etching | The RIE dry etching | The ammonium ceric nitrate wet etching |
| Processing characteristic | Etching agent is poisonous | Apparatus expensive, complex process | Etching agent is nontoxic, and technology is simple. |
In sum, it is little that the present invention has toxicity, and the processing technology characteristic of simple with greatly reducing the production cost of wet etching, is enhanced productivity significantly.
Description of drawings
Fig. 1 is a process chart of the present invention;
Fig. 2 is 30 minutes etching hole groove SEM figure (length of side 4 μ m);
Fig. 3 is 30 minutes etching hole groove SEM figure (length of side 40 μ m);
Fig. 4 is 60 minutes etching hole groove SEM figure.
The shape appearance figure that Fig. 5 peels off for Cr mask center.
Embodiment
Technological process of the present invention as shown in Figure 1.Photoetching process to Cr mask patterns processing and utilization standard: at first need on silicon chip, make masterplate by the figure of etching, the laggard exposure imaging of coated photoresist.Then in etching liquid, the Cr mask is carried out etching.Adopt ammonium ceric nitrate, 70% perchloric acid and water to mix and be made into (NH
4)
2Ce (NO
3)
5Etching liquid, in every 100ml etching liquid, the content of ammonium ceric nitrate is 5 grams～20 grams, the content of perchloric acid is: 1.5 milliliters～8 milliliters, all the other are water.In the etching, photoresist can be protected the figure of required reservation, and the figure transfer on the masterplate is to the Cr mask, last, and the silicon chip of being with mask is carried out the KOH wet etching.
Aspect technological process, processing is the photoetching process of utilizing standard to the Cr mask patterns: at first need make masterplate by the figure of etching on silicon chip, the laggard exposure imaging of coated photoresist.Follow in the solution Cr mask is carried out etching, utilize the photoresist protection to need the figure that keeps, the figure transfer on the masterplate is to the Cr mask, last, the silicon chip of being with mask is carried out the KOH wet etching.
Essence of the present invention is to use in silicon wet-etching technology Cr as mask material, and uses (NH
4)
2Ce (NO
3)
5, perchloric acid and water mixed liquor as etching liquid.
Example 1:
The a experimentation
1, cleaning Si sheet;
2, preparation sputter Cr mask, thickness 200nm, sputter equipment are the high frequency magnetic control sputtering system of ANELVA company;
3, on the Cr mask, utilize photoetching process to prepare figure, soon need on silicon wafer, make masterplate by the figure of etching, the laggard exposure imaging of coated photoresist;
4, at (NH
4)
2Ce (NO
3)
5In the etching liquid Cr mask is carried out etching, utilizes photoresist protection to need the figure that keeps, with the figure transfer on the masterplate to the Cr mask.(NH
4)
2Ce (NO
3)
5Solution only can react with the Cr that is not subjected to the photoresist protection, and does not all react with photoresist and Si.Every 100ml (NH
4)
2Ce (NO
3)
5In the etching liquid, the content of ammonium ceric nitrate is 15 grams, and the content of perchloric acid is: 5 milliliters, all the other are water.
5, the silicon wafer of mould layer uses KOH to carry out wet etching, use be dense KOH solution (KOH: H
2O=50g: 100ml).The wet etching system carries out 50 ℃ heated at constant temperature in HHS-1 type bain-marie, accuracy of temperature control ± 1 ℃.The silicon wafer φ 100mm that uses, N type, thickness 〉=510 μ m, resistivity 3 Ω cm, crystal orientation＜100 〉.
6, use (NH
4)
2Ce (NO
3)
5Etching liquid is removed the Cr mask.
The b result of the test
Shown in the SEM figure of Fig. 2, passed through 30 minutes etching, the square hole groove of the length of side 4 μ m has eroded away inverted pyramid type structure, and the pinnacle of a pagoda occurs.According to the characteristics of monocrystalline silicon wet etching, the wall of inverted pyramid should be＜111〉crystal orientation faces, with＜100〉the crystal orientation face is 53.7 ° inclination angle.The hole trough rim length of Fig. 3 is 40 μ m, and＜111〉face＜100〉projection on plane approximately is 15 μ m, can derive this moment degree of depth so and be approximately 15 * tan, 53.7 °=20.42 μ m.Through the measurement of step instrument, this moment, etching depth was 21.74 μ m; And Fig. 4 is the hole groove SEM figure of etching after 60 minutes, and＜111〉face＜100〉projection on plane approximately is 28 μ m, in like manner can release, the etching depth of this moment is 38.12 μ m, and the degree of depth that the step instrument tests out is 41.01 μ m.As mentioned before, the used etching liquid of test is 50 ℃ KOH (KOH: H
2O=50g: 100ml), etching speed is one minute 1 μ m in theory, and 60 minutes etching should be able to etch the figure about the degree of depth 60 μ m.The test etch rate has bigger gap with theoretical, and whether is still waiting further research because use the Cr mask that etching speed is slowed down.
Bigger white particle may be the KOH crystallization of not rinsing well in the groove of hole, and floccule should be K
2SiO
3Reaction products such as (potassium silicates), it is insoluble in the organic solvent, is easy to stick to silicon chip surface again, fails it is swept away during follow-up cleaning, just remains in the hole rooved face after the drying.Simultaneously, do not add IPA (isopropyl alcohol) in the etching liquid, so etching surface is not too smooth.
Example 2
The a experimentation
1, cleaning Si sheet;
2, preparation sputter Cr mask, thickness 50nm, sputter equipment are the high frequency magnetic control sputtering system of ANELVA company;
3, on the Cr mask, utilize photoetching process to prepare figure, soon need on silicon wafer, make masterplate by the figure of etching, the laggard exposure imaging of coated photoresist;
4, at (NH
4)
2Ce (NO
3)
5In the etching liquid Cr mask is carried out etching, utilizes photoresist protection to need the figure that keeps, with the figure transfer on the masterplate to the Cr mask.(NH
4)
2Ce (NO
3)
5Solution only can react with the Cr that is not subjected to the photoresist protection, and does not all react with photoresist and Si.Every 100ml (NH
4)
2Ce (NO
3)
5In the etching liquid, the content of ammonium ceric nitrate is 5 grams, and the content of perchloric acid is: 1.5 milliliters, all the other are water.
5, the silicon wafer of mould layer uses KOH to carry out wet etching, use be dense KOH solution (KOH: H
2O=50g: 100ml).The wet etching system carries out 50 ℃ heated at constant temperature in HHS-1 type bain-marie, accuracy of temperature control ± 1 ℃.The silicon wafer φ 100mm that uses, N type, thickness 〉=510 μ m, resistivity 3 Ω cm, crystal orientation＜100 〉.
6, use (NH
4)
2Ce (NO
3)
5Etching liquid is removed the Cr mask.
The b experimental result
The experimental result of the Cr mask of 50nm is alike in example 10 minutes, just because thickness is thinner relatively, so the figure that etching is come out is clear not as good as the Cr mask that uses 100nm.In addition, do not find tangible crackle through center after 60 minutes the etching in the etching liquid.
In this example, because (NH
4)
2Ce (NO
3)
5Etching liquid concentration is not high, so etching speed is slower.Soon figure will be transferred to the Cr mask from photoresist needs the long time.
Example 3
The a experimentation
1, cleaning Si sheet;
2, preparation sputter Cr mask, thickness 600nm, sputter equipment are the high frequency magnetic control sputtering system of ANELVA company;
3, on the Cr mask, utilize photoetching process to prepare figure, soon need on silicon wafer, make masterplate by the figure of etching, the laggard exposure imaging of coated photoresist;
4, at (NH
4)
2Ce (NO
3)
5In the etching liquid Cr mask is carried out etching, utilizes photoresist protection to need the figure that keeps, with the figure transfer on the masterplate to the Cr mask.(NH
4)
2Ce (NO
3)
5Solution only can react with the Cr that is not subjected to the photoresist protection, and does not all react with photoresist and Si.Every 100ml (NH
4)
2Ce (NO
3)
5In the etching liquid, the content of ammonium ceric nitrate is 20 grams, and the content of perchloric acid is: 8 milliliters, all the other are water.
5, the silicon wafer that will have the Cr mask uses KOH to carry out wet etching, use be dense KOH solution (KOH: H
2O=50g: 100ml).The wet etching system carries out 50 ℃ heated at constant temperature in HHS-1 type bain-marie, accuracy of temperature control ± 1 ℃.The silicon wafer φ 100mm that uses, N type, thickness 〉=510 μ m, resistivity 3 Ω cm, crystal orientation＜100 〉.
6, use (NH
4)
2Ce (NO
3)
5Etching liquid is removed the Cr mask.
The b experimental result
Adopt the sputtered film of 600nm, in the etching technics that does not need for a long time, can obtain comparatively good effect, be similar to example 1, and figure is comparatively clear.But because the sputtered film compact structure of 600nm, adhesion is strong, but its internal stress is also bigger.This makes silicon wafer relatively more fragile in the KOH of vigorous reaction solution, usually the generative center film situation advancing to split.In case the situation that the generative center film advances to split, the Si sheet will lose protection, figure occur and damage.As shown in Figure 5, behind 30 minutes wet etching, the center of silicon wafer is because the Cr mask advances to split to peel off and lost protection, and the figure of etching can't identification.
In this example, because (NH
4)
2Ce (NO
3)
5Etching liquid concentration is higher, so etching Cr mask speed is fast.
Claims (1)
1. silicon wet-etching technology, its step comprises:
(1), on the silicon chip of cleaning sputter Cr mask, the Cr mask thicknesses is 50nm～600nm;
(2), on the Cr mask, utilize photoetching process to prepare the photoresist figure;
(3), at (NH
4)
2Ce (NO
3)
5In the solution Cr mask is carried out etching, (NH
4)
2Ce (NO
3)
5The composition proportion of solution is: in the etching liquid of every 100ml, ammonium ceric nitrate is: 5 grams～20 grams, and perchloric acid is: 1.5 milliliters～8 milliliters, surplus is a water;
(4), use the silicon chip after KOH solution is etched to the Cr mask to carry out wet etching;
(5), use (NH
4)
2Ce (NO
3)
5Etching liquid is removed the Cr mask on the silicon chip.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100190524A CN100383932C (en) | 2005-07-05 | 2005-07-05 | Silicon wet-etching technology |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100190524A CN100383932C (en) | 2005-07-05 | 2005-07-05 | Silicon wet-etching technology |
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| CN100383932C true CN100383932C (en) | 2008-04-23 |
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Cited By (1)
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|---|---|---|---|---|
| CN101638781B (en) * | 2009-04-24 | 2011-08-17 | 中山大学 | Method for directly heating metal membrane to grow oxide nanowires in array-type arranged microcavity structure, and application thereof |
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| CN101812688B (en) * | 2009-02-19 | 2012-07-25 | 比亚迪股份有限公司 | Etching solution and etching method |
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