CN100426467C - Ultrathin gate pole oxidation layer and its growing method - Google Patents
Ultrathin gate pole oxidation layer and its growing method Download PDFInfo
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- CN100426467C CN100426467C CNB2004100918772A CN200410091877A CN100426467C CN 100426467 C CN100426467 C CN 100426467C CN B2004100918772 A CNB2004100918772 A CN B2004100918772A CN 200410091877 A CN200410091877 A CN 200410091877A CN 100426467 C CN100426467 C CN 100426467C
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- gate pole
- oxidation layer
- pole oxidation
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Abstract
The present invention provides a superthin gate oxide layer which comprises a porous silicon dioxide film with uniform thickness and holes. The present invention also provides a method for growing the superthin gate oxide layer, and the superthin gate oxide layer is formed on a silicon chip by using a direct current overlapping alternating current anode oxidation method and using deionized water as electrolyte. The superthin gate oxide layer provided by the present invention uses the direct current overlapping alternating current anode oxidation method, and regulates the electric field distribution condition of the electrolyte through overlapping alternating current with fixed frequency on direct current for anode oxidation, so that ions in the electrolyte obtain the opportunity for being redistributed, and finally, a superthin gate oxide layer which has better uniformity and low leakage current is obtained. The method can be widely applied to manufacturing various metal oxide semiconductors.
Description
[technical field]
The present invention is about a kind of method for semiconductor manufacturing, particularly a kind of method of the silica-based ultrathin gate pole oxidation layer of growing up.
[background technology]
Since the eighties in 20th century, metal-oxide semiconductor (MOS) (Metal Oxide Semiconductor, MOS) mainly made by silicon materials by transistorized gate.Yet along with the integrated circuit component size is constantly dwindled, more and more stricter to the quality requirement of gate pole oxidation layer, feasible research about the ultrathin gate pole oxidation layer manufacture method develops by leaps and bounds.At present, silicon based metal oxide semiconductor manufacture method mainly contains rapid thermal oxidation method (Rapid Thermal Oxidation), nitrogen doping oxidizing process (NitridedOxidation), liquid phase deposition (Liquid Phase Deposition) and anode oxidation method (AnodicOxidation) etc.Wherein, the gate pole oxidation layer of anode oxidation method growth has more high uniformity than the formed oxide layer of other method.
Conventional anodization method growth oxide layer technology is an electrolyte with deionized water or diluted acid usually, is negative electrode with Pt, and silicon is an anode, and the silicon anodic oxidation is formed silicon oxide layer.On April 7th, 1998, the 5th, 736, No. 454 patents of the U.S. of bulletin provided a kind of method that adopts the pure water anode oxidation method to make silicon dioxide layer on silicon base.This method may further comprise the steps: be anode with the silicon base, cell reaction at room temperature takes place, form silicon dioxide layer on silicon base; Silicon base is removed electrolyte; In atmosphere of inert gases, under 700 ℃～1000 ℃ temperature, heat this substrate a period of time, so that silicon dioxide layer density increases.See also Fig. 1, for being used for the electrolytic reaction system schematic diagram of this method.This system comprises an electrolysis tank 1; One programmable power supply 2; One program control electrometer 3; And the computer 4 of monitoring programmable power supply 2 and program control electrometer 3.Fill pure water as electrolyte 5 in electrolysis tank 1, and have a platinum sheet to make negative electrode 6, one chips to make anode 7, it immerses in pure water electrolyte 5.During cell reaction, current density is 1～100 μ A/cm
2, and with 10 μ A/cm
2For good.The gate pole oxidation layer that this method forms has less hole and preferred thickness uniformity.But since during electrolysis in pure water electrolyte non-uniform electric, make the gate pole oxidation layer uniformity be difficult to obtain further to improve, cause the gate pole oxidation layer leakage current to increase simultaneously.
No. 089102658 patent of TaiWan, China of announcing October 11 calendar year 2001 provides a kind of manufacture method of gate oxide film, comprises the steps: to heat in the vacuum semiconductor substrate, to remove natural oxide film; By containing oxygen plasma this semiconductor substrate of oxygen radical oxidation that gas produced that dissociates; The stop supplies oxygen radical; In oxygen molecule atmosphere, heat-treat then.This method is dissociated gas as oxidizing atmosphere to contain oxygen plasma, by the control energy of plasma, comes the oxidation of control thickness direction, with the controlled oxidation film thickness.And the oxidation reaction of horizontal direction is undertaken by oxygen-containing molecules atmosphere, and improves film density by it, and it is well controlled to form tool, less than the ultrathin membrane of 3nm.But, this manufacture method device therefor complexity, operating condition is harsh, and plasma oxidation is difficult to improve the uniformity of oxide-film, influences the quality of gate oxide film.
In view of this, provide a kind of method of the gate pole oxidation layer that uniformity is higher, leakage current is low of growing up real for necessary.
[summary of the invention]
Formed gate pole oxidation layer uniformity is difficult to improve in the prior art in order to overcome, and the more high deficiency of leakage current, the object of the present invention is to provide the method for the ultrathin gate pole oxidation layer that a kind of uniformity of growing up is higher, leakage current is low.
For achieving the above object, the invention provides a kind of method of the ultrathin gate pole oxidation layer of growing up, it may further comprise the steps:
One silicon is provided;
Silicon is inserted in the electrolyte, is anode with it, and is negative electrode with platinum;
Adopting the direct current fixed frequency alternating current that superposes is power supply, and anodic oxidation forms ultrathin gate pole oxidation layer on silicon.
And described electrolyte adopts deionized water or diluted acid.
Holding current density constant in the described power supply galvanization, the current density range that adopts are 5～500 μ A/cm
2, and with 10～50 μ A/cm
2For good.
Described silicon adopts p type polysilicon chip.
The described direct current fixed frequency alternating current that superposes is realized by dc pulse superposition power supply or single-phase AC-DC overlaying power.
In addition, also can further heat-treat the ultrathin gate pole oxidation layer that forms.
Compared with prior art, the present invention adopts DC stacked AC anode oxidation method growth ultrathin gate pole oxidation layer, alternating current by stack fixed frequency on the anodic oxidation direct voltage, regulate electrolyte intermediate ion migration rate and direction, make the electrolyte intermediate ion obtain the chance of redistribution, thereby effectively improve electric field uneven distribution phenomenon in the electrolyte, improve thickness evenness and hole density, finally obtain the ultrathin gate pole oxidation layer that uniformity is better, leakage current is low.
[description of drawings]
Below in conjunction with accompanying drawing the present invention is described in further detail.
Fig. 1 is the electrolysis system schematic diagram of growth ultrathin gate pole oxidation layer in the prior art.
Fig. 2 is the electrolysis system schematic diagram of growth ultrathin gate pole oxidation layer of the present invention.
Fig. 3 A～3C is the electrolysis principle schematic diagram of growth ultrathin gate pole oxidation layer of the present invention.
[embodiment]
See also Fig. 2, be the electrolysis system schematic diagram of the ultrathin gate pole oxidation layer that is used to grow up.This electrolysis system 10 comprises an electrolysis tank 11, fills electrolyte 12 in it; One anode 13; One negative electrode 14; One power supply 15, it can supply the power supply of whole system; One electrostatic generator 16, it provides scope adjustable electrostatic pressure, as 0～60V, and can provide constant voltage or constant current density; And an ac generator 17, it provides fixed frequency, alternating current that amplitude range is little.Wherein, electrolyte 12 adopts deionized water or diluted acid.Anode 13 adopts silicon, and as required with in its all or part of immersion electrolyte 12, and negative electrode 14 adopts the platinum sheet.In electrolysis system 10, electrostatic generator 16 can adopt in parallel or series system with the connecting mode of ac generator 17, powers for electrolysis tank 11 simultaneously, and cell reaction takes place.In the electrolytic process, deionized water is dissociated into H
+With OH
-, under electric field action, migrate to anode and cathode then respectively, following electrode reaction correspondingly takes place on platinum cathode 14 and silicon anode 13:
Cathode reaction: 2H
++ 2e
-=H
2
Anode reaction: Si+4OH
-=SiO
2+ 2H
2O+4e
-
As a result, anodic oxidation forms porous silica layer on silicon, is gate pole oxidation layer (figure does not show), thereby OH in the electrolyte 12
-Formation to gate pole oxidation layer has considerable influence.
In conjunction with said apparatus, the method for growth ultrathin gate pole oxidation layer provided by the present invention is described, it may further comprise the steps:
(1) provides a silicon.This silicon can be selected from materials such as p type polysilicon chip, then it is carried out polishing and heat treatment, removes natural oxidizing layer and obtains smooth surface, is beneficial to the later stage anodized.
(2) silicon being inserted in the electrolyte 12, is anode 13 with it, and is negative electrode 14 with platinum.It is electrolyte 12 that present embodiment adopts deionized water, and the silicon that is about to after step (1) is handled is inserted in the deionized water, and as the anode 13 of cell reaction, and negative electrode 14 adopts the platinum sheet.As required, silicon can all or part of immersion deionized water in.
(3) energising, anodic oxidation forms ultrathin gate pole oxidation layer on silicon.Be about to anode 13 and negative electrode 14 energized, silicon is carried out anodized, the ultra-thin silica membrane of growing up on its surface.Wherein, the electricity that led to adopts the superpose little amplitude alternating current of a fixed frequency of direct current.This direct current is by electrostatic generator 16 supplies, and the little amplitude alternating current of fixed frequency is by ac generator 17 supplies.Because when current density is too high, can increase the burn-out rate of oxide-film, thereby, in electrolytic process of the present invention, holding current density constant during cell reaction, and be controlled at 5～500 μ A/cm
2Between, and with 10～50 μ A/cm
2For good.For realizing DC stacked AC power, adopt silicon-controlled voltage regulation, on the DC power supply basis, add the pulse power, its make-to-break ratio is 2: 1～5: 1; Also can adopt single-phase AC-DC overlaying power, at this moment, the proportion of the peak swing voltage of the voltage of electrostatic generator 16 and ac generator 17 can adopt 2: 1～8: 1.See also people such as Tu Yichuan about AC-DC overlaying power " electroplate and cover with paint, lacquer, colour wash, etc. ", V19 (2), 2000,13-17, the relevant introduction of " hard anodizing of aluminium alloy under the constant current density " literary composition.
In addition, for improving the quality and the density of ultrathin gate pole oxidation film layer, can further heat-treat it.
Usually,,, will occur directly wearing and satisfy effect (Direct Tunneling Effect), and cause the gate pole oxidation layer leakage current to increase if the uniformity of oxide layer is relatively poor when gate oxide layer thickness during less than 3nm.And the gate pole oxidation layer that the present invention grows up is a super thin oxide layer, and thickness is between 1～3nm.For avoiding producing above-mentioned phenomenon, must promote the uniformity of oxide layer.Thereby the present invention adopts DC stacked AC anode oxidation method, by the little amplitude alternating current of stack one fixed frequency on the direct voltage that applies when the anodic oxidation.So, direct voltage can provide anodic oxidation time institute's energy requirement, the little amplitude alternating current of stack then provides ion redistribution chance, to form the higher ultrathin gate pole oxidation layer of uniformity, reduces its leakage current.
See also Fig. 3 A～3C, be the electrolysis principle schematic diagram of growth ultrathin gate pole oxidation layer of the present invention.The horizontal line thickness is represented leakage current among the figure, and the thick more expression leakage current of horizontal line is big more, and vice versa.When cell reaction takes place, under direct voltage, as voltage during greater than 1 volt, identical with the conventional anodization method, the non-uniform electric phenomenon appears between anode 13 and negative electrode 14, cause that electric field strong and weak and direction distribute also inhomogeneous in the electrolyte 12, thereby hydroxide ion 18 migration rates and direction are inhomogeneous, place at electric-field strength, the ion migration rate is very fast, cause on some direction the ion migration more, thereby more hydroxide ion 18 is gathered in the relevant position on silicon, make its oxidation aggravation, shown in oxidation position L1 and L2 in the gate pole oxidation layer 19 among Fig. 3 A.If it is constant to continue this electrostatic pressure, the oxidation of oxidation position L1 and L2 will continue to deepen, and then become the comparatively serious place of leakage current.When behind stack one little amplitude alternating current on the direct voltage, voltage is decreased to and is lower than 1 volt, at this moment, oxidation rate descends relatively, Electric Field Distribution changes, hydroxide ion 18 obtains the redistribution chance, original degree of oxidation is deepened, shown in 19 oxidation position L3 of gate pole oxidation layer among Fig. 3 B and L4 than the weak position oxidation.Certainly, the minimum position of electric field influence is arranged also, shown in oxidation position L5 among the figure.Like this, by little amplitude alternating current to galvanic fine setting effect, change Electric Field Distribution in the whole electrolyte, the chance that makes hydroxide ion 18 obtain to redistribute, to remedy the inhomogeneous of oxide layer, finally can obtain the gate pole oxidation layer 19 (shown in Fig. 3 C) of thickness and hole uniformity, its thickness is 1 nanometer～3 nanometers, hole diameter is 5 nanometers～20 nanometers, and hole density is 10
11Individual/cm
2～1.5 * 10
12Individual/cm
2The better oxide layer of this uniformity embodies than low leakage characteristic.
Therefore, in the method for growth ultrathin gate pole oxidation layer provided by the invention, migration has the fine setting effect to the alternating current of little amplitude to the electrolyte intermediate ion in whole electrolytic process, it constantly adjusts ion migration rate and direction, make the electrolyte intermediate ion obtain the chance of redistribution, thereby can effectively improve electric field uneven distribution phenomenon in the electrolyte, obtain finally that uniformity is better, the gate pole oxidation layer of low-leakage current.
Claims (8)
1. the method for the ultrathin gate pole oxidation layer of growing up, it may further comprise the steps:
One silicon is provided;
Silicon is inserted in the electrolyte, is anode with it, and is negative electrode with platinum;
Energising, anodic oxidation forms ultrathin gate pole oxidation layer on silicon;
It is characterized in that: the electricity that led to adopts the superpose alternating current of a fixed frequency of direct current.
2. the method for growth ultrathin gate pole oxidation layer as claimed in claim 1 is characterized in that: described electrolyte adopts deionized water or diluted acid.
3. the method for growth ultrathin gate pole oxidation layer as claimed in claim 1 is characterized in that: holding current density constant in the described galvanization.
4. the method for growth ultrathin gate pole oxidation layer as claimed in claim 3 is characterized in that: the current density range of described energising is 5～500 μ A/cm
2
5. the method for growth ultrathin gate pole oxidation layer as claimed in claim 4 is characterized in that: the current density range of described energising is 10～50 μ A/cm
2
6. the method for growth ultrathin gate pole oxidation layer as claimed in claim 1 is characterized in that: described silicon adopts p type polysilicon chip.
7. as the method for each described growth ultrathin gate pole oxidation layer of claim 1 to 6, it is characterized in that:
The superpose alternating current of a fixed frequency of described direct current is realized by dc pulse superposition power supply or single-phase AC-DC overlaying power.
8. the method for growth ultrathin gate pole oxidation layer as claimed in claim 7 is characterized in that: further the ultrathin gate pole oxidation layer that forms is heat-treated.
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| CN100426467C true CN100426467C (en) | 2008-10-15 |
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| US9218958B2 (en) * | 2013-12-10 | 2015-12-22 | Infineon Technologies Ag | Method for forming a semiconductor device |
| CN105632896B (en) * | 2016-01-28 | 2018-06-15 | 深圳市华星光电技术有限公司 | The method for manufacturing thin film transistor (TFT) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5736454A (en) * | 1997-03-20 | 1998-04-07 | National Science Council | Method for making a silicon dioxide layer on a silicon substrate by pure water anodization followed by rapid thermal densification |
| CN2418137Y (en) * | 2000-05-17 | 2001-02-07 | 吴永敏 | Ac.-dc. superpositioned aluminium-foil strip anode oxygenation apparatus |
| US6352939B1 (en) * | 1999-06-10 | 2002-03-05 | National Science Council | Method for improving the electrical properties of a gate oxide |
-
2004
- 2004-12-25 CN CNB2004100918772A patent/CN100426467C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5736454A (en) * | 1997-03-20 | 1998-04-07 | National Science Council | Method for making a silicon dioxide layer on a silicon substrate by pure water anodization followed by rapid thermal densification |
| US6352939B1 (en) * | 1999-06-10 | 2002-03-05 | National Science Council | Method for improving the electrical properties of a gate oxide |
| CN2418137Y (en) * | 2000-05-17 | 2001-02-07 | 吴永敏 | Ac.-dc. superpositioned aluminium-foil strip anode oxygenation apparatus |
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