Form the method for cvd film
Technical field
The present invention relates to technical field of manufacturing semiconductors, particularly a kind of method that on semiconductor wafer, forms CVD (chemical vapor deposition) film.
Background technology
In super large-scale integration (ULSI) manufacturing process,, begin to expand in vertical direction by increasing the method for the deposit number of plies along with constantly dwindling of circuit size.The layer of these increases plays various effect in device, circuit, mainly can be used as the interlayer dielectric, metal line, resistance, surface passivation layer of gate electrode, multilayer wiring etc.For little figure, the condition influence on its resolving power subject wafer surface is very big, along with feature dimensions is reduced to submicron order, chip manufacturing process is more and more urgent to the requirement of fabricating low-defect-density, specification of quality to deposition film is also more and more higher, the homogeneity of its thickness not only can have influence on down normally carrying out of step process, also can have influence on the electrical property and the mechanical property of device, and and then has influence on the yield rate and the output of device.
So-called deposit is meant that a kind of material is deposited on technological process on the wafer surface with physics mode, the method of thin-film deposition has chemical vapor deposition (CVD, Chemical Vapor Deposition) method and physical vapour deposition (PVD, Physical Vapor Deposition) method two big classes.Wherein, chemical vapor deposition is that chemical substance mixed being incorporated under the gaseous state in reaction chamber of containing required atom of film or molecule reacts, and its atom or molecular deposition are assembled in wafer surface, film forming process.Chemical vapor deposition is not because of its technology comparatively simply, needs high vacuum, is convenient to prepare combination product, the deposition rate height, and the various films of deposit have advantages such as excellent step covering performance and are widely used in the manufacturing of semiconducter device.
At present, CVD technology has more more options, can work at atmospheric or low pressure, can use cold wall or hot wall system, and the energy supply source also can be selected thermal radiation and plasma body for use.But no matter be any, identical step is all arranged, wafer is packed in the reaction chamber, and be heated to preset temperature, feed corresponding reactant gases, these reactant gasess arrive the substrate surface generation chemical reaction of heating, form the solid film and the gaseous product of wishing formation, again gaseous product is discharged by the exhaust system of system, take out wafer at last.In this reaction process, will inevitably be on the base-plates surface of reaction chamber for cold wall system, will inevitably on the inwall of reaction chamber and base-plates surface, accumulate resultant for hot wall system.Repeatedly after the deposit, the coming off of these reactants will cause the staining of wafer, and forms defective, needs frequent cleaning reaction chamber, to avoid polluting wafer for this reason.For removing the deposit on undesirable inwall and the pedestal easily, application number a kind of self-cleaning processing method that has been 20050242061 U.S. Patent Publication, it feeds clean air according to the deposit type that will remove in reaction chamber, make the deposit gasification, again it is discharged reaction chamber.This automatically cleaning process has reduced the number of times of chamber cleaning, has improved the quality of produced film to a certain extent.
How to remove some pollutions that in deposition process, produce but reckon without in this method.In the reality, though cleaning or automatically cleaning reaction chamber, also can form defective because of the instability of deposition process or the too fast surface of speed of reaction at wafer.If reaction indoor air flow shakiness in the reaction process, specific period when especially deposit finishes, no longer feed reactant gases in the reaction chamber, and only the existing gas in the reaction chamber is discharged, reaction is still being carried out in this process, variation but must take place in the gas flow system in the reaction chamber, and the improper deposit of reactant very easily appears in this moment, shows as reactant gases and condenses in wafer surface and form protruding defective.In addition,, also be prone to reactant gases condensing on wafer surface, form protruding defective if the deposit speed of reaction is too fast.The protruding defective synoptic diagram of Fig. 1 on wafer surface, forming in the prior art, as shown in Figure 1, utilize plasma enhanced chemical vapor deposition method (PECVD, Plasma EnhancedChemical Vapor Deposition) the borosilicate glass film (BSG) of on silicon substrate, growing, 101 improper protruding defectives that form on the wafer surface that are deposited on that are reactant wherein, this defective causes cvd film in uneven thickness, degradation, and then have influence on normally carrying out of back technology.Fig. 2 A to Fig. 2 B is the device profile map of the protruding defective effect etching technics of cvd film appearance in the explanation prior art; Shown in Fig. 2 A, protruding defective 101 appears when growing CVD film 102 on wafer 103, and this projection defective 101 causes the figure deformation of institute's etching in etching technics subsequently, shown in Fig. 2 B, when wafer surface is smooth when not having defective, etching institute perforate 104 neat in edge, figure is complete; When the etching tapping is positioned at protruding fault location, can cause institute's perforate 105 edge deformations serious.The etching figure deformation that these protruding defectives cause can cause device performance to descend, and yield rate reduces.
Summary of the invention
Therefore, the object of the present invention is to provide a kind of method that on semiconductor wafer, forms cvd film, this method feeds the gas that does not participate in the deposit reaction of different amounts by the different steps at deposition process, under the situation that does not increase technology difficulty, reduce the protruding defective on the wafer surface effectively, solved the problem that easily produces defective in the existing C VD film deposition process.
For achieving the above object, a kind of method that forms cvd film on semiconductor wafer provided by the invention comprises:
A inserts semiconductor wafer in the reaction chamber of CVD system;
B feeds first gas in the reaction chamber;
C introduces deposit cvd film in the reaction chamber with energy;
When the d deposit is finished, feed second gas;
E finishes deposit, takes out wafer.
Wherein, described CVD system is the plasma enhanced CVD system.
Wherein, described cvd film is the borosilicate glass film; Described first gas is B
2H
6, SiH
4And N
2The mixed gas of O.
Wherein, described second gas is a kind of in nitrogen, hydrogen, argon gas and the helium; To between the 30000sccm, the time of feeding is between 5 seconds to 300 seconds at 1000sccm for its flow.
The another kind that the present invention has identical or a relevant art feature forms the method for cvd film on semiconductor wafer, comprising:
A places semiconductor wafer in the reaction chamber of CVD system;
B feeds first gas and second gas in the reaction chamber simultaneously;
C introduces deposit cvd film in the reaction chamber with energy;
The d deposit strengthens the flow of described second gas when finishing;
E finishes deposit, takes out wafer.
Wherein, described CVD system is the plasma enhanced CVD system.
Wherein, described cvd film is the borosilicate glass film; Described first gas is B
2H
6, SiH
4And N
2The mixed gas of O.
Wherein, described second gas is a kind of in nitrogen, hydrogen, argon gas and the helium, its flow in described step b at 10sccm between the 10000sccm.
Wherein, between the 30000sccm, the feeding time is between 5 seconds to 300 seconds to the flow range of described second gas enlargement discharge in described steps d at 1000sccm.
Compared with prior art, the present invention has the following advantages:
By when deposit is finished, feeding the gas that does not participate in the deposit reaction, solved prior art when deposit finishes, reaction is still being carried out, but no longer feed reactant gases, only existing gas is discharged, make the gas flow system in the reaction chamber that variation take place, thereby be prone to improper deposit, cause wafer surface the problem of protruding defective to occur.The gas that does not participate in the deposit reaction that the present invention feeds when deposit is finished has been kept original gas flow system on the one hand, the stability that keeps the reaction indoor air flow, also play the effect of diluting reaction gas on the other hand, can obviously reduce the protruding defective of wafer surface, effectively improve the quality of the cvd film of institute's deposit, improve the performance and the yield rate of device.
In addition, by feed the gas that does not participate in the deposit reaction in deposition process, pressure that conditioned reaction is indoor and reactive deposition speed have reduced reactive deposition speed, have improved the good control to the cvd film deposit, have further improved the quality of the cvd film of institute's deposit.
Description of drawings
The protruding defective synoptic diagram of Fig. 1 on wafer surface, forming in the prior art;
The synoptic diagram of protruding defective effect etching technics appears in Fig. 2 A and Fig. 2 B for the existing cvd film of explanation;
Fig. 3 is a wafer surface blemish distribution situation synoptic diagram behind the prior art deposit cvd film;
Fig. 4 is the schema of cvd film formation method first embodiment of the present invention;
Fig. 5 is the schema of cvd film formation method second embodiment of the present invention;
Fig. 6 is a wafer surface blemish distribution schematic diagram behind the application cvd film deposition process deposit cvd film of the present invention.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing.
Cvd film because air-flow shakiness or reaction pressure and the improper reactant gases that easily causes of rate adaptation condense in wafer surface, forms protruding defective in deposition process.Fig. 3 is the wafer surface situation behind the prior art deposit cvd film, and a large amount of defectives 101 that form on the wafer among the figure have certain areal distribution as can be seen, the final stage gas flow system of this and the deposit direct relation that changed.The method that the present invention forms cvd film is the gas that does not participate in the deposit reaction that feeds different amounts by the different times in deposit, realizes regulating the speed of deposit and the purpose of steady air flow system, has improved the growth quality of cvd film.Wherein, in the first embodiment of the present invention,, realized the stable of gas flow system, reduced zonal protruding defective by feeding the gas that does not participate in the deposit reaction period of finishing in deposit; In the second embodiment of the present invention, then do not participate in the gas of deposit reaction except finish the feeding in period in deposit, in deposition process, also fed a certain amount of this gas, under the prerequisite that does not change the reaction chamber total gas pressure, to reduce the speed of deposit, reduce protruding defective, further improved the growth quality of cvd film.Below method of the present invention is described in further detail.
Fig. 4 is the schema of cvd film deposition process first embodiment of the present invention.
Referring to Fig. 4, the first embodiment of the present invention is to utilize PECVD deposit growth borosilicate glass film (BSG) on wafer, at first will treat the wafer handling (S401) to the CVD reaction chamber of deposit bsg film, again wafer will be heated to preset temperature (S402), perform the preceding preparation of deposit.
Then, feed required first gas (S403) of reaction according to the film type of wanting deposit, deposit is bsg film in the present embodiment, so the first used gas is B
2H
6, N
2O and SiH
4Mixed gas.
Then, after the reactant gases that feeds reaches steady state, introduce energy, realize deposit (S404).Supposing used in the present embodiment is the PECVD system, then introduces glow discharge by radio frequency, produces plasma body, realizes deposit under low pressure and low temperature.
By the time after deposit is finished, stop to feed first gas (S405).At this moment, glow discharge does not finish, and reaction is still being carried out, and residual gas is still held the discharge chamber that continues.If do not take measures, then the gas flow system in the chamber certainly will change, and improper deposit easily takes place, and causes wafer surface protruding defective to occur.Exactly because this gas flow system changes, just can form the regional protruding defective that distributes in wafer surface.At this point, the present invention has adopted when deposit is finished the method that feeds the indoor gas flow system of the second gas stopping reaction that do not participate in the deposit reaction.
Finish deposit, when stopping to feed reactant gases, feeding second gas (S406), general employing does not participate in the gas of deposit reaction, as N
2, its flow can for example be 5000sccm at 1000sccm between the 30000sccm, the feeding time can be between 5 seconds to 300 seconds, as 60 seconds.The adding of this step, kept the stable of Primordial Qi fluid system on the one hand, on the other hand because the charging into of a large amount of second gases, also diluted the concentration of reactant gases greatly, prevented effectively that from two aspects reactant gases from the condensing of wafer surface, obviously having improved the quality of the cvd film of institute's deposit.Figure 6 shows that the wafer surface situation that when the deposit bsg film is finished, adds the gas that does not participate in the deposit reaction, the defective 101 that can see its wafer surface obviously reduces, the raising of this cvd film quality helps normally carrying out of back technology, has improved the yield rate of device.
At last, finish deposit, take out wafer (S407).
Fig. 5 is the schema of cvd film deposition process second embodiment of the present invention.
Referring to Fig. 5, the implementation method of the second embodiment of the present invention is as follows:
At first also be that the wafer handling of desiring deposit is arrived in the CVD reaction chamber (S501), be heated to predetermined temperature (S502).
Then, first gas (S503) according to the film type feeding reaction needed of wanting deposit feeds second gas in the certain flow scope simultaneously in the present embodiment, generally select the gas (S504) that does not participate in the deposit reaction for use.As, the deposit bsg film then feeds the first gas B that reacts
2H
6, N
2O and SiH
4Mixed gas the time, can feed N2, its flow at 10sccm in the 10000sccm scope, as 1000sccm.The adding of this step is because for bsg film, and the content of boron has certain limit to require, and as between 3% to 10%, for example is 7%.This has just determined doping agent B
2H
6With SiH
4, N
2Throughput ratio between the O.And in the process of deposit bsg film, for keeping stable gas flow system, the total pressure in the chamber will remain unchanged.Like this, total pressure is definite in the chamber on the one hand, and three kinds of flow rate of reactive gas are more definite than also on the other hand, if do not participate in the adding of the gas of deposit reaction this moment, it is too fast then can speed of reaction to occur, easily causes reactant gases the condensing of wafer surface, and forms defective.In order to improve this point, in the present embodiment, added gas N
2, keep chamber total pressure and reaction gas flow than constant situation under, diluted reactant gases, reduced deposition rate, realized reducing the purpose of protruding defective.
Then, after the reactant gases that feeds and the distribution of gas in chamber that do not participate in the deposit reaction reach steady state, introduce energy, realize deposit (S505).Supposing used in the present embodiment is the PECVD system, then introduces glow discharge by radio frequency, produces plasma body, realizes deposit under low pressure and low temperature.
Finish deposit, when stopping to feed first gas (S506), be stablizing of the indoor gas flow system of holding chamber, strengthened second gas flow (S507) that feeds in the former deposition process, its scope can be at 1000sccm between the 30000sccm, for example be 5000sccm, the feeding time can be between 5 seconds to 300 seconds, as 60 seconds.
At last, finish deposit, take out wafer (S508).
In the present embodiment, by in deposition process and deposit feed the gas that does not participate in the deposit reaction of different flow when finishing, realized respectively the adjusting of deposition rate and stable to gas flow system.Reduce the protruding defective on cvd film surface significantly, improved the quality of cvd film effectively.
Among the above-described embodiment, used CVD system is PECVD, in other embodiments of the invention, can also be other CVD systems such as normal pressure, low pressure and high density plasma.
Among the above-described embodiment, institute's deposit be bsg film, in other embodiments of the invention, can also be other cvd films such as silicon oxide film, silicon nitride film and polysilicon film.
Among the above-described embodiment, the second used gas is nitrogen, in other embodiments of the invention, can also be other gases such as hydrogen, helium, argon gas.
Though the present invention with preferred embodiment openly as above; but it is not to be used for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can make possible change and modification, so protection scope of the present invention should be as the criterion with the scope that claim of the present invention was defined.