Control cmp time method and system
Technical field
The present invention relates to semiconductor fabrication, particularly a kind of control cmp time method and system.
Background technology
In the current semiconductor fabrication process; Can use cmp (CMP) technology under a lot of situation, such as shallow trench isolation from the polishing of (STI) silica, local interconnected (LI) silica polishing, the polishing of LI tungsten, the polishing of inter-level dielectric (ILD) silica and copper polishing etc.
Fig. 1 is the structural representation of existing chemical mechanical polishing device.As shown in Figure 1, suppose that this chemical mechanical polishing device comprises that altogether three covers grind subsystem, i.e. subsystem 1, subsystem 2 and subsystem 3; Wherein, comprise in each subsystem: abrasive disk, be fixed in grinding pad and slurry supply pipe on the abrasive disk.The slurry supply pipe is used to export slurry.This chemical mechanical polishing device also comprises four grinding heads, after being used for loading and unloading wafer successively, moves on the corresponding subsystem.
When grinding, at first with wafer to be ground attached on the grinding head, move to the subsystem top that will grind, to be ground of wafer contacted with grinding pad; Then, abrasive disk and grinding head all are rotated by counter clockwise direction under the driving of motor, but both rotary speeies are different, and grinding head also carries out radial motion along the diametric(al) of grinding pad; Simultaneously, the lapping liquid supply pipe is carried slurry to grinding pad, and chemical action and mechanism through slurry make flattening wafer surface.Need to prove that according to the difference of material to be ground, the concrete composition of slurry is also with difference, in addition, the material of grinding pad and pattern etc. are also with difference.Move to loading and unloading bit stripping wafer after the grinding again.
This chemical mechanical polishing device comprises that also a sub-systems 4 as loading and unloading wafer position, is contained in this wafer on the grinding head in this position, rotates to subsystem 1, subsystem 2 or subsystem 3 successively, when unloading, rotates to subsystem 4 and unloads.
In practical application; Suppose that a certain wafer need carry out three times altogether and grind; This wafer will grind according to the order of subsystem 1, subsystem 2 and subsystem 3 successively so; The material of being responsible for according to each subsystem grinding identical or different, each subsystem can adopt identical or different slurry and grinding pad.For each subsystem, in a processing procedure, the grinding technics that it adopted is identical with parameter, can grind one or more batches wafer successively, and the wafer of each batch has a plurality of.
When each sub-systems that adopts chemical mechanical polishing device is ground wafer; For each subsystem; It all is a slice a slice grinding wafer successively, and in this process, the grinding pad of this subsystem can suffer the loss of loss and each grinding head; For the wafer of same grinding thickness, the milling time that in same subsystem, needs may be inequality.Therefore, proposed a kind of lifting CMP course control method for use at present, this control method is respectively applied on each subsystem, the time control of grinding during to the identical thickness of the grinding wafer that grinds successively.
Because the setting of chemical mechanical polishing device; The process that each sub-systems is ground the control sheet successively is a continuous process; Because the loss of subsystem in process of lapping; The performance of subsystem has change over time, so for same subsystem, the process of grinding last wafer can influence the process of follow-up grinding wafer.At this moment; Just need to adopt lifting CMP course control method for use respectively the abrasive parameters (being mainly milling time) of each sub-systems to be made amendment; So that the wafer thickness that same subsystem is ground is identical, in same processing procedure, improve the yield rate of wafer in different time sections.
Promote the CMP course control method for use and in fact be exactly a feedback control system each sub-systems is carried out the FEEDBACK CONTROL of milling time respectively, this feedback control system be arranged in the control section of chemical mechanical polishing device and each sub-systems directly mutual.This feedback control system is as shown in Figure 2.
This feedback control system comprises concentrated measurement module, dynamic model module and grinding control module at least, wherein,
Concentrate measurement module, be used for measuring respectively each sub-systems of chemical mechanical polishing device is ground current wafer in the time of setting actual grinding thickness value, then this measurement result is sent to the dynamic model module;
The dynamic model module stores dynamic model, is used for calculating according to the dynamic model that this measurement result substitution that receives is provided with, and obtains the time segment value that each sub-systems is ground next wafer respectively, sends to the grinding control module;
The grinding control module is used for the time segment value according to each system's next wafer of grinding that receives from the power model module, respectively the time segment value of each next wafer of sub-systems grinding is adjusted.
Like this, each sub-systems just adopts adjusted time segment value to grind when grinding next wafer respectively, makes that the wafer thickness of in different time sections, grinding is identical.
Particularly, in the dynamic model module, dynamic model will be set, the principle of setting is:
Grind current wafer time segment value=(the target grinding thickness of the actual grinding thickness-last wafer of desirable grinding wafer thickness+last wafer)/grinding wafer rate equation (1)
Wherein, The target grinding thickness grinding wafer speed of the desirable grinding wafer thickness in the formula (1), last wafer is (for different subsystems; This speed can be inequality or identical) all be settings, storage in advance, the actual grinding thickness of last wafer then is what measure.
During dynamic model in the dynamic model module specifically is set, the dynamic model below adopting:
Grind next wafer time segment value=(the target grinding thickness of the actual grinding thickness-last wafer of desirable grinding wafer thickness+last wafer)+(the actual grinding thickness of the actual grinding thickness-current wafer of current wafer)/grinding wafer rate equation (2)
Wherein, The actual grinding thickness of the desirable grinding wafer thickness in the formula (2), the target grinding thickness of last wafer, current wafer and grinding wafer speed all are the value that is provided with; Storage in advance; And the actual grinding thickness value of current wafer is current measuring, and the target grinding thickness of last wafer is to measure when grinding last wafer and buffer memory.
Can find out from above-mentioned narration; When concrete the realization; The lifting CMP course control method for use of prior art need all be provided with the dynamic model of a complicacy to each subsystem; And calculate according to the dynamic model of the complicacy that is provided with respectively, obtain the time segment value of next wafer of grinding of each subsystem, and then indicate each subsystem to go adjustment.Time segment value to next wafer of grinding of each system carries out complicated calculating and adjustment so respectively, and the not high and control more complicated of control efficiency is difficult for realizing.
In addition; When feeding back; Feed back respectively for each grinding head, because in process of lapping, the grinding head that for same subsystem, uses each time might not be identical; So the result of last feedback also can't really react the loss of current subsystem, so also not high to the accuracy of subsystem adjustment according to feedback result.Perhaps adopt to obtain the feedback result of identical grinding head on subsystem subsystem is adjusted, consumed time also can be long.
Summary of the invention
In view of this, the present invention provides a kind of control cmp time method, and the efficient of this method raising control cmp time and fairly simple is higher in relatively shorter time inner control milling time and ratio of precision.
The present invention also provides a kind of system that controls the cmp time, and this system can improve the control efficient of cmp time and fairly simple.
For achieving the above object, the technical scheme of the embodiment of the invention specifically is achieved in that
A kind of control cmp time method, this method is applied in the control procedure to each sub-systems in the chemical mechanical polishing device, stores the milling time segment value that each sub-systems is ground current wafer, and this method also comprises:
Measure each sub-systems respectively and grind the thickness of current wafer, obtain the actual (real) thickness value that each sub-systems is ground current wafer respectively;
Adopt to grind the Q factor values of each sub-systems of ratio calculation of target thickness value of the current wafer of grinding of actual (real) thickness value and the setting of current wafer respectively;
With the average of the Q factor values of each sub-systems as Q ' factor values;
After each sub-systems of Q ' factor values and storage being ground product between the milling time segment value of current wafer and grinding the time segment value of next wafer as each sub-systems respectively, offer each sub-systems and carry out.
The number of described each sub-systems is 3.
The milling time segment value that described each sub-systems is ground current wafer calculates the initial value that perhaps is provided with for adopting said method.
After the initial value of said setting equals actual grinding thickness that desirable grinding wafer thickness adds last wafer; Deduct the value that the target grinding thickness of last wafer obtains; Divided by grinding wafer speed, wherein, the target grinding thickness grinding wafer speed of desirable grinding wafer thickness, last wafer is settings again; Storage in advance, the actual grinding thickness of last wafer then are what measure.
A kind of system that controls the cmp time, be arranged in the control section of chemical mechanical polishing device and each sub-systems directly mutual, comprise at least:
Concentrate measurement module, be used for measuring respectively each sub-systems of chemical mechanical polishing device is ground current wafer in the time of setting actual grinding thickness value, then this measurement result is sent to the dynamic model module;
The dynamic model module of the Q factor; Store the dynamic model of the Q factor; Be used for obtaining the Q factor values of each sub-systems according to the grinding thickness ratio of the grinding thickness of current wafer and current goal wafer; Obtain Q ' factor values after averaging, will grind time period of current wafer then on dutyly to obtain grinding the time segment value of next wafer, send to the grinding control module with Q ' factor values;
The grinding control module is used for the time segment value according to each system's next wafer of grinding that receives from the power model module, respectively the time segment value of each next wafer of sub-systems grinding is adjusted.
The time segment value of the current wafer of said grinding is that the time segment value that is provided with in advance or calculate a wafer is stored.
Visible by technique scheme; The present invention has defined dynamic model again; Introduced the notion of the Q ' factor, for each subsystem, the time segment value that grinds next wafer is on duty with Q ' factor values for the time period of grinding current wafer; Q ' factor values is the average Q factor values of each sub-systems that calculates, and the Q factor values of each sub-systems is the grinding thickness of current wafer and the grinding thickness ratio of current goal wafer.Like this, fairly simple when different subsystems is calculated the milling time of next wafer when the milling time of each sub-systems is controlled than the formula (2) of prior art, can improve the efficient of control cmp time.Therefore, method provided by the invention has improved the efficient of control cmp time and fairly simple.Simultaneously, this Q ' be exactly Zong the feedback of the different grinding heads of factor grinding efficiency after having passed through three sub-systems, rather than corresponding single subsystem need be as single subsystem feedback, and is higher in relatively shorter time inner control milling time and ratio of precision.
Description of drawings
Fig. 1 is the structural representation of existing chemical mechanical polishing device;
Fig. 2 is the feedback structure sketch map of prior art;
Fig. 3 is a control cmp time method flow chart provided by the invention;
Fig. 4 is the system architecture sketch map of control cmp time provided by the invention.
The specific embodiment
For making the object of the invention, technical scheme and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, the present invention is done further explain.
Can find out from prior art; When adopting existing lifting CMP course control method for use to realize the lower and complicated reason of efficient to the milling time control procedure of each sub-systems in the chemical mechanical polishing device; For each subsystem; All need set up the dynamic model (formula (2) just) of a complicacy, calculate this subsystem of milling time Duan Houzai control of next wafer then respectively.Because formula (2) more complicated, when calculating, need be applied to a plurality of parameters (that comprise storage in advance and current measuring), so caused the efficient of this subsystem of subsequent control lower and complicated.In addition, owing to when calculating, need a plurality of parameters, so the inaccurate degree of accuracy that all can have influence on the subsequent control subsystem of each parameter causes the degree of accuracy of final etching subsystem also not high.
Prior art is when feeding back; Feed back respectively for each grinding head; Because in process of lapping, for each subsystem, the grinding head that uses each time might not be identical; So the result of last feedback also can't really react the loss of current subsystem, so also not high to the accuracy of subsystem adjustment according to feedback result.Perhaps adopt to obtain the feedback result of identical grinding head on subsystem subsystem is adjusted, consumed time can be long.
In order to overcome the problems referred to above; The present invention improves dynamic model again; Introduced the notion of the Q ' factor, for each subsystem, the time segment value that grinds next wafer is on duty with Q ' factor values for the time period of grinding current wafer; Q ' factor values is the average Q factor values of each sub-systems that calculates, and the Q factor values of each sub-systems is the grinding thickness of current wafer and the grinding thickness ratio of current goal wafer.Like this; When the milling time of each sub-systems is controlled; When different subsystems is calculated the milling time of next wafer; Than the formula (2) of prior art, dynamic model is fairly simple and parameter that relate to is fewer, thereby the efficient and the accuracy that have improved the control cmp time also improve greatly.
For Q ' provided by the invention Jiu Shi Zong the factor in fact corresponding the Coupled Feedback of the grinding efficiencies after having passed through three sub-systems of the different grinding heads in the device shown in Figure 1; That is to say that Q ' factor pair is answered is the grinding efficiency that different conditions and the different grinding heads of three sub-systems combine.Than prior art; Method provided by the invention has been considered the influence (loss obtains when grinding wafer through detection subsystem) of adjacent grinding processing procedure between four grinding heads; So just can improve feedback efficiency; And the grinding feedback of prior art to be each system independently accept a last wafer, feedback efficiency is lower.
Below lifting embodiment is elaborated to method and system provided by the invention.
Fig. 3 is a control cmp time method flow chart provided by the invention; This method is applied in the control procedure to each sub-systems in the chemical mechanical polishing device; Store the milling time segment value that each sub-systems is ground current wafer in advance, its concrete steps are:
Each sub-systems is ground current wafer according to the milling time section of indication in step 301, the chemical mechanical polishing device;
Behind step 302, the current grinding wafer, measure the thickness that each sub-systems is ground current wafer respectively, obtain the actual (real) thickness value that each sub-systems is ground current wafer respectively;
In this step,, then measure the actual (real) thickness value of the current wafer of grinding of three sub-systems if this method is applied to chemical mechanical polishing device shown in Figure 1;
In this step, how measuring each sub-systems, to grind the thickness of current wafer be prior art, no longer tired here stating;
Step 303, calculate the Q factor values of each sub-systems respectively;
In this step, the target thickness value formula (3) that adopts Q=to grind the actual (real) thickness value/current wafer of grinding of current wafer calculates the Q factor values of each sub-systems;
"/" in the formula (3) expression divided by implication, the target thickness value of grinding current wafer be pre-set and storage;
In this step,, then need calculate the Q factor values of three sub-systems if this method is applied to chemical mechanical polishing device shown in Figure 1;
Step 304, calculate Q ' factor values;
In this step, Q ' is the average of the Q factor values of each sub-systems;
In this step, if this method is applied to chemical mechanical polishing device shown in Figure 1, then Q ' is that the Q factor values sum of three sub-systems is again divided by three;
Step 305, the milling time segment value that grinds current wafer according to each sub-systems of Q ' factor values and storage calculate respectively after each sub-systems grinds the time segment value of next wafer, offer each sub-systems, change step 301 over to and continue to carry out;
In this step, time segment value=each sub-systems of each next wafer of sub-systems grinding is ground the milling time segment value * Q ' formula (4) of current wafer;
In this step, " * " expression wherein multiply by;
In this step, if this method is applied to chemical mechanical polishing device shown in Figure 1, then need calculate the time segment value of next wafer of three sub-systems, at this moment, three sub-systems are ground the milling time segment value of current wafer can be identical or different.
In this process,, just in a processing procedure process, grind the milling time segment value of wafer for the first time for the milling time segment value of the current wafer of initial grinding of each system; Can be provided with in advance; Also can adopt the formula (1) of prior art to obtain, wherein, the actual grinding thickness value of a last wafer and the target grinding thickness value of a last wafer can adopt the control sheet to measure; The control sheet is when in a processing procedure process, formally grinding wafer, to measure and use wafer.
Fig. 4 is the system architecture sketch map of control cmp time provided by the invention; Be arranged in the control section of chemical mechanical polishing device and each sub-systems directly mutual, comprise the dynamic model module and the grinding control module of concentrated measurement module, the Q factor at least; Wherein
Concentrate measurement module, be used for measuring respectively each sub-systems of chemical mechanical polishing device is ground current wafer in the time of setting actual grinding thickness value, then this measurement result is sent to the dynamic model module;
The dynamic model module of the Q factor stores the dynamic model of the Q factor, is used to adopt this measurement result of receiving to calculate according to the dynamic model of the Q factor that is provided with, and obtains the time segment value that each sub-systems is ground next wafer, sends to the grinding control module;
The grinding control module is used for the time segment value according to each system's next wafer of grinding that receives from the power model module, respectively the time segment value of each next wafer of sub-systems grinding is adjusted.
In this process; The dynamic model module adopts this measurement result receive to carry out calculation process according to the dynamic model of the Q factor that is provided with: the Q factor values that obtains each sub-systems according to the grinding thickness ratio of the grinding thickness of current wafer and current goal wafer; Obtain Q ' factor values after averaging, will grind the time period time segment value that obtains grinding next wafer with Q ' factor values on duty of current wafer then.
Particularly, the time segment value that grinds current wafer is that the time segment value that is provided with in advance or calculate a wafer is stored, and the time segment value of the current wafer of grinding of different sub-systems can be identical or different.
In system shown in Figure 4, the milling time segment value for the current wafer of initial grinding of each system of employing just grinds for the first time the milling time segment value of wafer in a processing procedure process; Can be provided with in advance; Also can adopt the formula (1) of prior art to obtain, wherein, the actual grinding thickness value of a last wafer and the target grinding thickness value of a last wafer can adopt the control sheet to measure; The control sheet is when in a processing procedure process, formally grinding wafer, to measure and use wafer.
More than lift preferred embodiment; The object of the invention, technical scheme and advantage have been carried out further explain, and institute it should be understood that the above is merely preferred embodiment of the present invention; Not in order to restriction the present invention; All within spirit of the present invention and principle, any modification of being done, be equal to replacement and improvement etc., all should be included within protection scope of the present invention.