CN102915912A - Method for forming sacrifice oxide layer on silicon carbide surface - Google Patents
Method for forming sacrifice oxide layer on silicon carbide surface Download PDFInfo
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- CN102915912A CN102915912A CN2012103559348A CN201210355934A CN102915912A CN 102915912 A CN102915912 A CN 102915912A CN 2012103559348 A CN2012103559348 A CN 2012103559348A CN 201210355934 A CN201210355934 A CN 201210355934A CN 102915912 A CN102915912 A CN 102915912A
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Abstract
The invention relates to a method for forming a sacrifice oxide layer on a silicon carbide surface, which comprises the following steps of: 1, cleaning a SiC (silicon carbide) wafer by acid solution; 2, cleaning the SiC wafer by hydrofluoric acid solution with the volume by volume concentration of 5 percent to 30 percent; 3, placing the SiC wafer into an oxidizing furnace, filling mixed gas of inert gas and oxygen, which is used as protection gas, and heating the oxidizing furnace to an oxidizing temperature; 4, filling the oxygen into the oxidizing furnace and preserving the temperature to carry out thermal oxidation; and 5, filling the inert gas into the oxidizing furnace and cooling the SiC wafer to the room temperature from the oxidizing temperature. The method has the beneficial effects that the mixed gas of the inert gas and the oxygen is used as the protection gas, so that the thickness uniformity of the oxide layer is good; the oxidizing speed is improved and the process time can be shortened; and the formed oxide layer has a good surface flatness and the reliability and the finished product rate of a device can be improved.
Description
Technical field
What the present invention relates to is a kind of method that forms sacrificial oxide layer, specifically relates to a kind of method that forms sacrificial oxide layer at silicon carbide.
Background technology
Carborundum (SiC) material is the third generation wide bandgap semiconductor materials that grows up afterwards from first generation elemental semiconductors (Si) and second generation compound semiconductor materials (GaAs, GaP, InP etc.).The SiC material is particularly suitable for making microwave high power, high pressure, high temperature, anti-irradiated electrons device owing to having the characteristics such as broad-band gap, high critical breakdown electric field, high heat conductance, high electronics saturation drift velocity, has widely in all sectors of the national economy and uses.Current, the development of SiC device has become study hotspot.
Need aluminium in the manufacture process of SiC device, the p-type foreign ions such as boron are injected in the N-shaped epitaxial loayer, and activate the ion that injects by the high temperature anneal more than 1600 ℃.Implantation and high annealing all can affect surface topography to SiC surface injury, form one deck damage layer.Surface damage layer can directly have influence on electric property and the reliability of device.In order to improve the surface topography of SiC behind Implantation and the activated at, improve device performance, need to carry out surface treatment to SiC.Surface treatment method commonly used has two kinds at present: (1) utilizes dry etching to remove the damage layer on SiC surface, and the advantage of the method is that the process time is short, but can cause new damage to the SIC surface in the process of dry etching, can't remove the damage layer fully; (2) form one deck sacrificial oxide layer by thermal oxidation on the SiC surface first, adopt again the mode of wet etching to remove sacrificial oxide layer, the method can be removed the damage layer on SiC surface fully, but the thickness evenness to sacrificial oxide layer requires very high, if in uneven thickness after removing sacrificial oxide layer, the SiC surface can occur uneven, causes device creepage to increase.Because the oxidation rate of SiC is very low, in order to remove surface damage layer fully, form the chronic of sacrificial oxide layer simultaneously.In the process that forms sacrificial oxide layer, oxidizing condition is very important, and annealing conditions comprises: oxidizing temperature, oxidization time, heating rate, protective gas type, flow and air pressure.Studies show that in a large number, annealing temperature is higher, and annealing time is longer, and oxidation rate is higher, but high temperature can make the oxidized surface roughness descent, affects the oxidated layer thickness uniformity; The type of protective gas and air pressure can have influence on the uniformity of oxidation rate and oxide layer in oxidizing process.Oxidizing condition commonly used adopts inert gas as protective gas usually at present, and the process time is longer.
In sum, in order to improve SiC device reliability and rate of finished products, reduce production costs.Method at silicon carbide formation sacrificial oxide layer commonly used also has many defectives at present, and the oxidizing condition of sacrificial oxide layer also has improved necessity.
Summary of the invention
What the present invention proposed is a kind of method that forms sacrificial oxide layer at silicon carbide, its objective is that oxidation rate is high, oxidated layer thickness good uniformity, the method for oxidation of surfacing in order to solve the existing above-mentioned deficiency of prior art.
Technical solution of the present invention: a kind of method that forms sacrificial oxide layer at silicon carbide, the method may further comprise the steps:
1) use acid solution to clean the SiC wafer;
2) use the hydrofluoric acid solution of 5%-30% volume by volume concentration to clean the SiC wafer;
3) the SiC wafer is put into oxidation furnace, be filled with the gaseous mixture of inert gas and oxygen as protective gas, oxidation furnace is warmed up to oxidizing temperature;
4) in oxidation furnace, be filled with oxygen, keep temperature to carry out thermal oxidation;
5) in oxidation furnace, be filled with inert gas, the SiC wafer is cooled to room temperature by oxidizing temperature.
Beneficial effect of the present invention: the gaseous mixture that 1) adopts inert gas and oxygen is as protective gas, and the thickness evenness of oxide layer is good.2) oxidation rate improves, and can shorten the process time.3) the oxide layer surface smoothness that forms is better, can improve device reliability and rate of finished products.
Embodiment
Below in conjunction with specific embodiment, further set forth the present invention, should understand these embodiment and only be used for explanation the present invention and be not used in and limit the scope of the invention.
Embodiment 1
Step 1) uses the acid solution mixed solution to clean the SiC wafer.Described acid solution is sulfuric acid or hydrochloric acid.This step can be removed the impurity that the SiC wafer surface is adhered to, and prevents that impurity from reacting with SiC in oxidizing process, forms defective on the surface, also can avoid impurity effect sacrificial oxide layer uniformity and evenness.
Step 2) use the hydrofluoric acid solution of 5% volume by volume concentration to clean the SiC wafer.This step can be removed the natural oxidizing layer of SiC wafer, avoids natural oxidizing layer to affect sacrificial oxide layer uniformity and evenness.
Step 3) is put into oxidation furnace with the SiC wafer, is filled with the gaseous mixture of inert gas and oxygen as protective gas, and oxidation furnace is warmed up to oxidizing temperature.The effect that is filled with inert gas in this step is to prevent that the residual gas in SiC and the oxidation furnace from reacting; in the inhomogeneous oxide layer of Surface Creation; and then affect the quality of sacrificial oxide layer; for the flow that guarantees inert gas in the quality of oxide layer protective gas is greater than oxygen flow; described inert gas is argon gas; the flow of inert gas is 1 liter/min of clock in this step, and the flow-rate ratio of inert gas and oxygen gas is 10:1.Flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer in this step, flow too little or too big city cause sacrificial oxide layer evenness variation.The effect that is filled with oxygen is in SiC Surface Creation one deck oxide layer as thin as a wafer in temperature-rise period, the surface smoothness of the sacrificial oxide layer that raising forms in oxidation stage, improve the oxidation rate of oxidation stage, the flow of oxygen is 0.1 liter/min of clock in this step, flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer, flow too little or too big city cause sacrificial oxide layer evenness variation.Air pressure is 0.5bar in this step, the too low uniformity that can affect oxide layer of air pressure.
Step 4) is filled with oxygen in oxidation furnace, keep temperature to carry out oxidation.The flow of oxygen is 0.1 liter/min of clock in this step, the too high surface smoothness that can affect SiC of air pressure, and air pressure is too low.Air pressure is 0.5bar in this step, and air pressure is too low can be affected the uniformity of oxide layer and reduce oxidation rate.The mode of oxidizing that can adopt in this step comprises dry-oxygen oxidation and wet-oxygen oxidation, and the dry-oxygen oxidation oxidation rate is low, and the oxide layer surface smoothness is good, and the wet-oxygen oxidation oxidation rate is high, but the oxide layer surface smoothness is relatively poor.The scope of oxidizing temperature is 1000 ℃ in this step, and oxidizing temperature more high oxidization rate is higher, but the oxide layer surface smoothness is poorer.
Step 5) is filled with inert gas in oxidation furnace, the SiC wafer is cooled to room temperature by oxidizing temperature.The range of flow of inert gas is 0.1 liter/min of clock in this step, and flow is larger, and rate of temperature fall is faster.
Embodiment 2
Step 1) uses the acid solution mixed solution to clean the SiC wafer.Described acid solution is nitric acid.This step can be removed the impurity that the SiC wafer surface is adhered to, and prevents that impurity from reacting with SiC in oxidizing process, forms defective on the surface, also can avoid impurity effect sacrificial oxide layer uniformity and evenness.
Step 2) use the hydrofluoric acid solution of 30% volume by volume concentration to clean the SiC wafer.This step can be removed the natural oxidizing layer of SiC wafer, avoids natural oxidizing layer to affect sacrificial oxide layer uniformity and evenness.
Step 3) is put into oxidation furnace with the SiC wafer, is filled with the gaseous mixture of inert gas and oxygen as protective gas, and oxidation furnace is warmed up to oxidizing temperature.The effect that is filled with inert gas in this step is to prevent that the residual gas in SiC and the oxidation furnace from reacting; in the inhomogeneous oxide layer of Surface Creation; and then affect the quality of sacrificial oxide layer; for the flow that guarantees inert gas in the quality of oxide layer protective gas is greater than oxygen flow; described inert gas is argon nitrogen; the flow of inert gas is 20 liter/mins of clocks in this step, and the flow-rate ratio of inert gas and oxygen gas is 2:1.Flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer in this step, flow too little or too big city cause sacrificial oxide layer evenness variation.The effect that is filled with oxygen is in SiC Surface Creation one deck oxide layer as thin as a wafer in temperature-rise period, the surface smoothness of the sacrificial oxide layer that raising forms in oxidation stage, improve the oxidation rate of oxidation stage, the flow of oxygen is 10 liter/mins of clocks in this step, flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer, flow too little or too big city cause sacrificial oxide layer evenness variation.Air pressure is 1bar in this step, the too low uniformity that can affect oxide layer of air pressure.
Step 4) is filled with oxygen in oxidation furnace, keep temperature to carry out oxidation.The flow of oxygen is 10 liter/mins of clocks in this step, the too high surface smoothness that can affect SiC of air pressure, and air pressure is too low.Air pressure range is 1bar in this step, and air pressure is too low can be affected the uniformity of oxide layer and reduce oxidation rate.The mode of oxidizing that can adopt in this step comprises dry-oxygen oxidation and wet-oxygen oxidation, and the dry-oxygen oxidation oxidation rate is low, and the oxide layer surface smoothness is good, and the wet-oxygen oxidation oxidation rate is high, but the oxide layer surface smoothness is relatively poor.The scope of oxidizing temperature is 1400 ℃ in this step, and oxidizing temperature more high oxidization rate is higher, but the oxide layer surface smoothness is poorer.
Step 5) is filled with inert gas in oxidation furnace, the SiC wafer is cooled to room temperature by oxidizing temperature.The flow of inert gas is 20 liter/mins of clocks in this step, and flow is larger, and rate of temperature fall is faster.
Embodiment 3
Step 1) uses the acid solution mixed solution to clean the SiC wafer.Described acid solution is the mixture of sulfuric acid and hydrochloric acid, ratio 1:1.This step can be removed the impurity that the SiC wafer surface is adhered to, and prevents that impurity from reacting with SiC in oxidizing process, forms defective on the surface, also can avoid impurity effect sacrificial oxide layer uniformity and evenness.
Step 2) use the hydrofluoric acid solution of 15% volume by volume concentration to clean the SiC wafer.This step can be removed the natural oxidizing layer of SiC wafer, avoids natural oxidizing layer to affect sacrificial oxide layer uniformity and evenness.
Step 3) is put into oxidation furnace with the SiC wafer, is filled with the gaseous mixture of inert gas and oxygen as protective gas, and oxidation furnace is warmed up to oxidizing temperature.The effect that is filled with inert gas in this step is to prevent that the residual gas in SiC and the oxidation furnace from reacting; in the inhomogeneous oxide layer of Surface Creation; and then affect the quality of sacrificial oxide layer; for the flow that guarantees inert gas in the quality of oxide layer protective gas is greater than oxygen flow; the flow of inert gas is 10 liter/mins of clocks in this step; flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer, flow too little or too big city cause sacrificial oxide layer evenness variation.The effect that is filled with oxygen is in SiC Surface Creation one deck oxide layer as thin as a wafer in temperature-rise period, the surface smoothness of the sacrificial oxide layer that raising forms in oxidation stage, improve the oxidation rate of oxidation stage, the flow of oxygen is 5 liter/mins of clocks in this step, flow directly has influence on surface smoothness and the oxidation rate of sacrificial oxide layer, flow too little or too big city cause sacrificial oxide layer evenness variation.Air pressure is 0.6bar in this step, the too low uniformity that can affect oxide layer of air pressure.
Step 4) is filled with oxygen in oxidation furnace, keep temperature to carry out oxidation.The range of flow of oxygen is 6 liter/mins of clocks in this step, the too high surface smoothness that can affect SiC of air pressure, and air pressure is too low.Air pressure is 0.6bar in this step, and air pressure is too low can be affected the uniformity of oxide layer and reduce oxidation rate.The mode of oxidizing that can adopt in this step comprises dry-oxygen oxidation and wet-oxygen oxidation, and the dry-oxygen oxidation oxidation rate is low, and the oxide layer surface smoothness is good, and the wet-oxygen oxidation oxidation rate is high, but the oxide layer surface smoothness is relatively poor.The scope of oxidizing temperature is 1200 ℃ in this step, and oxidizing temperature more high oxidization rate is higher, but the oxide layer surface smoothness is poorer.
Step 5) is filled with inert gas in oxidation furnace, the SiC wafer is cooled to room temperature by oxidizing temperature.The flow of inert gas is 10 liter/mins of clocks in this step, and flow is larger, and rate of temperature fall is faster.
Claims (10)
1. method that forms sacrificial oxide layer at silicon carbide, it is characterized in that: the method may further comprise the steps:
1) use acid solution to clean the SiC wafer;
2) use the hydrofluoric acid solution of 5%-30% volume by volume concentration to clean the SiC wafer;
3) the SiC wafer is put into oxidation furnace, be filled with the gaseous mixture of inert gas and oxygen as protective gas, oxidation furnace is warmed up to oxidizing temperature;
4) in oxidation furnace, be filled with oxygen, keep temperature to carry out thermal oxidation;
5) in oxidation furnace, be filled with inert gas, the SiC wafer is cooled to room temperature by oxidizing temperature.
2. a kind of method that forms sacrificial oxide layer at silicon carbide according to claim 1 is characterized in that described acid solution comprises sulfuric acid, hydrochloric acid, nitric acid and mixed solution thereof.
3. a kind of method that forms sacrificial oxide layer at silicon carbide according to claim 1 is characterized in that described inert gas comprises argon gas and nitrogen.
4. according to a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1, it is characterized in that as the inert gas of protective gas and the flow-rate ratio of oxygen gas be 10-2:1.
5. according to a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1, the flow that it is characterized in that described inert gas is 0.1 liter/min of clock-20 liter/min clock.
6. according to a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1, the flow that it is characterized in that oxygen is 0.1 liter/min of clock-10 liter/min clock.
7. a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1 is characterized in that the mode of thermal oxidation comprises dry-oxygen oxidation and wet-oxygen oxidation; Oxidizing temperature is 1000-1400 ℃.
8. a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1 is characterized in that air pressure range is 0.5-1bar in intensification and the oxidizing process.
9. a kind of method that forms sacrificial oxide layer at silicon carbide claimed in claim 1 is characterized in that the type of SiC wafer comprises 6H-SiC, 4H-SiC.
10. a kind of high annealing method for the manufacture of silicon carbide device according to claim 1 is characterized in that the type of SiC wafer is included in the epitaxial wafer of one or more layers carborundum films of having grown on the silicon carbide substrates.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104810278A (en) * | 2014-01-29 | 2015-07-29 | 北大方正集团有限公司 | Sacrifice oxide layer formation method |
| CN106158583A (en) * | 2015-04-01 | 2016-11-23 | 北大方正集团有限公司 | A kind of silicon wafer forms the method for sacrificial oxide layer |
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| US20080128709A1 (en) * | 2000-03-24 | 2008-06-05 | Vanderbilt University | Inclusion of nitrogen at the silicon dioxide-silicon carbide interface for passivation of interface defects |
| CN101979160A (en) * | 2010-05-21 | 2011-02-23 | 北京天科合达蓝光半导体有限公司 | Method for cleaning pollutants on surface of silicon carbide wafer |
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Patent Citations (4)
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| CN1263355A (en) * | 1999-02-10 | 2000-08-16 | 日本电气株式会社 | Method for making thin-grid silicon oxide layer |
| US20080128709A1 (en) * | 2000-03-24 | 2008-06-05 | Vanderbilt University | Inclusion of nitrogen at the silicon dioxide-silicon carbide interface for passivation of interface defects |
| CN101030609A (en) * | 2007-04-04 | 2007-09-05 | 厦门大学 | Theta-doped 4HSiC avalanche ultraviolet photoelectric detector and its production |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104810278A (en) * | 2014-01-29 | 2015-07-29 | 北大方正集团有限公司 | Sacrifice oxide layer formation method |
| CN106158583A (en) * | 2015-04-01 | 2016-11-23 | 北大方正集团有限公司 | A kind of silicon wafer forms the method for sacrificial oxide layer |
| CN106158583B (en) * | 2015-04-01 | 2019-10-15 | 北大方正集团有限公司 | A kind of method that silicon wafer forms sacrificial oxide layer |
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Application publication date: 20130206 |