Summary of the invention
Introduced the concept of a series of reduced forms in the summary of the invention part, this will further describe in specific embodiment part.Summary of the invention part of the present invention does not also mean that key feature and the essential features that will attempt to limit technical scheme required for protection, does not more mean that the protection domain of attempting to determine technical scheme required for protection.
For solve in the prior art owing to the higher limit of polishing time and lower limit set bad cause can't the effective monitoring polishing time situation, the invention provides a kind of method for dynamically adjusting the event horizon of chemically mechanical polishing, comprise the following steps: 1) collect the polishing time of all wafers in the historical time section P; The initial lower limit Ctrl1 of the polishing time of determining first batch of polished batch wafers according to quantity and the described polishing time of described wafer
RWith initial higher limit Ctrl2
R, wherein, the time range that is limited by described initial lower limit and described initial higher limit is the time range that covers the described polishing time of the described wafer more than 80% in the described historical time section;
2) select at least 4 built-in testing control wafers and described test control wafer polished; Collect respectively the thickness T H_Blank1_n of described test control wafer before carrying out described polishing, finish thickness T H_Blank2_n and actual polishing time T_Blank_n after the described polishing;
3) draw respectively the actual polishing speed RR11_n of described test control wafer by following formula:
RR11_n=(TH_Blank1_n-TH_Blank2_n)/T_Blank_n,
n=1,2,3,4,...
And calculate the mean value of RR11n as the polishing speed RR11 of described test control wafer;
4) at least 4 polished wafers of random choose from described first batch of polished batch wafers, the arithmetic mean of instantaneous value that calculates the actual (real) thickness of described polished wafer before carrying out described polishing is carrying out thickness Pre1 before the described polishing as described first batch of polished batch wafers;
5) target polished speed RR10 and the target thickness Pre0 of described first batch of polished batch wafers before carrying out described polishing of the described test control wafer of collection;
6) model of the reference lower limit value Ctrl1 of the described first batch of polished batch wafers polishing time of foundation calculating and reference upper level value Ctrl2 is as follows:
Ctrl1=T1+(RR10-RR11)*K2+(Pre1-Pre0)*K3
Ctrl2=T2+(RR10-RR11)*K2+(Pre1-Pre0)*K3
Wherein, T1 is 40~50 seconds, and T2 is 60~70 seconds; K2 is 0.075~0.175 second minute/dust, and K3 is 0.01~0.03 second/dust; Then
7) obtain lower limit T_min and the higher limit T_max of the polishing time of described first batch of polished batch wafers in polishing process according to following mode:
If Ctrl1<Ctrl1
R, T_min=Ctrl1 then
R, otherwise, T_min=Ctrl1;
If Ctrl2<Ctrl2
R, T_max=Ctrl2 then, otherwise, T_max=Ctrl2
R
Wherein, described Ctrl1
RUnit be second, described Ctrl2
RUnit be second, the unit of described Ctrl1 is second, the unit of described Ctrl2 is second, and the unit of described TH_Blank1_n is dust, and the unit of described TH_Blank2_n is dust, the unit of described T_Blank_n is minute, the unit of described RR11_n is A/min, and the unit of described RR11 is A/min, and the unit of described RR10 is A/min, the unit of described Pre1 is dust, and the unit of described Pre0 is dust.
The invention provides a kind of method for dynamically adjusting the event horizon of chemically mechanical polishing, comprise the following steps:
1) polishing time of the interior all wafers of collection historical time section P '; The initial lower limit Ctrl1 of the polishing time of determining current polished batch wafers according to quantity and the described polishing time of described wafer
R' and initial higher limit Ctrl2
R', wherein, the time range that is limited by described initial lower limit and described initial higher limit is the time range that covers the described polishing time of the described wafer more than 80% in the described historical time section;
2) select at least 4 polished wafers in the batch wafers in the past; Collect respectively the thickness T H1_n ' of described polished wafer before carrying out described polishing, finish thickness T H2_n ' and actual polishing time T_n ' after the described polishing;
3) draw respectively the actual polishing speed RR21_n ' of described polished wafer by following formula:
RR21_n’=(TH1_n’-TH2_n’)/T_n’,
n=1,2,3,4,...
And calculate the mean value of RR21_n ' as the polishing speed RR21 ' of described last batch wafers;
4) at least 4 polished wafers of random choose from described current polished batch wafers, the arithmetic mean of instantaneous value that calculates the actual (real) thickness of described polished wafer before carrying out described polishing is carrying out thickness Pre1 ' before the described polishing as described current polished batch wafers;
5) target polished speed RR20 ' and the target thickness Pre0 ' of described current polished batch wafers before carrying out described polishing of the described last batch wafers of collection;
6) model of the reference lower limit value Ctrl1 ' of the described current polished batch wafers polishing time of foundation calculating and reference upper level value Ctrl2 ' is as follows:
Ctrl1’=T3’+(RR20’-RR21’)*K1’+(Pre1’-Pre0’)*K3’
Ctrl2’=T4’+(RR20’-RR21’)*K1’+(Pre1’-Pre0’)*K3’
Wherein, T3 ' is 37~47 seconds, and T4 ' is 61~71 seconds; K1 ' is 0.012~0.032 second minute/dust, and K3 ' is 0.01~0.03 second/dust; Then
7) obtain lower limit T_min ' and the higher limit T_max ' of the polishing time of described current polished batch wafers in polishing process according to following mode:
If Ctrl1 '<Ctrl1
R', T_min '=Ctrl1 then
R', otherwise, T_min '=Ctrl1 ';
If Ctrl2 '<Ctrl2
R', T_max '=Ctrl2 ' then; Otherwise, T_max '=Ctrl2
R';
Wherein said Ctrl1
R' unit be second, described Ctrl2
R' unit be second, the unit of described Ctrl1 ' is second, the unit of described Ctrl2 ' is second, and the unit of described TH1_n ' is dust, and the unit of described TH2_n ' is dust, the unit of described T_n ' is minute, the unit of described RR21_n ' is A/min, and the unit of described RR21 ' is A/min, and the unit of described RR20 ' is A/min, the unit of described Pre1 ' is dust, and the unit of described Pre0 ' is dust.
The invention provides a kind of method for dynamically adjusting the event horizon of chemically mechanical polishing, comprise the following steps:
1) collect historical time section P " polishing time of interior all wafers; The initial lower limit Ctrl1 of the polishing time of determining first batch of polished batch wafers according to quantity and the described polishing time of described wafer
R" and initial higher limit Ctrl2
R", wherein, the time range that is limited by described initial lower limit and described initial higher limit is the time range that covers the described polishing time of the described wafer more than 80% in the described historical time section;
2) select at least 4 built-in testing control wafers and described test control wafer polished; Collect respectively the thickness T H_Blank1_n of described test control wafer before carrying out described polishing ", finish the thickness T H_Blank2_n after the described polishing " and actual polishing time T_Blank_n ";
3) draw respectively the actual polishing speed RR11_n of described test control wafer by following formula ":
RR11_n”=(TH_Blank1_n”-TH_Blank2_n”)/T_Blank_n”,
n=1,2,3,4,...
And calculate RR11_n " mean value as the polishing speed RR11 of described test control wafer ";
4) at least 4 polished wafers of random choose from described first batch of polished batch wafers, the arithmetic mean of instantaneous value that calculates the actual (real) thickness of described polished wafer before carrying out described polishing is carrying out thickness Pre1 before the described polishing as described first batch of polished batch wafers ";
5) the target polished speed RR10 of the described test control wafer of collection " and the target thickness Pre0 of described first batch of polished batch wafers before carrying out described polishing ";
6) set up to calculate the reference lower limit value Ctrl1 of described first batch of polished batch wafers polishing time " and reference upper level value Ctrl2 " model as follows:
Ctrl1”=T1”+(RR10”-RR11”)*K2”+(Pre1”-Pre0”)*K3”
Ctrl2”=T2”+(RR10”-RR11”)*K2”+(Pre1”-Pre0”)*K3”
Wherein, T1 " be 40~50 seconds, T2 " be 60~70 seconds; K2 " be 0.075~0.175 second minute/dust, K3 " be 0.01~0.03 second/dust; Then
7) obtain the lower limit T_min of the polishing time of described first batch of polished batch wafers in polishing process according to following mode " and higher limit T_max ":
If Ctrl1 "<Ctrl1
R", T_min then "=Ctrl1
R", otherwise, T_min "=Ctrl1 ";
If Ctrl2 "<Ctrl2
R", T_max then "=Ctrl2 ", otherwise, T_max "=Ctrl2
R";
Wherein said Ctrl1
R" unit be second, described Ctrl2
R" unit be second; described Ctrl1 " unit be second, described Ctrl2 " unit be second, described TH_Blank1_n " unit be dust, described TH_Blank2_n " unit be dust; described T_Blank_n " unit be minute, described RR11_n " unit be A/min described RR11 " unit be A/min described RR10 " unit be A/min; described Pre1 " unit be dust, described Pre0 " unit be dust;
8) for second batch and follow-up polished batch wafers, select at least 4 polished wafers in the batch wafers in the past; Collect respectively the thickness T H1_n of described polished wafer before carrying out described polishing " ', finish the thickness T H2_n after the described polishing " ' and actual polishing time T_n " ';
9) draw respectively the actual polishing speed RR21_n of described polished wafer by following formula " ':
RR21_n”’=(TH1_n”’-TH2_n”’)/T_n”’,
n=1,2,3,4,...
And calculate RR21_n " ' mean value as the polishing speed RR21 of described last batch wafers " ';
10) at least 4 polished wafers of random choose from described current polished batch wafers, the arithmetic mean of instantaneous value that calculates the actual (real) thickness of described polished wafer before carrying out described polishing is carrying out thickness Pre1 before the described polishing as described current polished batch wafers " ';
11) the target polished speed RR20 of the described last batch wafers of collection " ' and the target thickness Pre0 of described current polished batch wafers before carrying out described polishing " ';
12) set up calculating the reference lower limit value Ctrl1 of described current polished batch wafers polishing time " model of ' and reference upper level value Ctrl2 " ' is as follows:
Ctrl1”’=T3”’+(RR20”’-RR21”’)*K1”’+(Pre1”’-Pre0”’)*K3”’
Ctrl2”’=T4”’+(RR20”’-RR21”’)*K1”’+(Pre1”’-Pre0”’)*K3”’
Wherein, T3 " ' be 37~47 seconds, T4 " ' be 61~71 seconds; K1 " ' be 0.012~0.032 second minute/dust, K3 " ' be 0.01~0.03 second/dust; Then
13) obtain the lower limit T_min of the polishing time of described current polished batch wafers in polishing process according to following mode " ' and higher limit T_max " ':
If Ctrl1 " '<Ctrl1
R", T_min then " '=Ctrl1
R", otherwise, T_min " '=Ctrl1 " ';
If Ctrl2 " '<Ctrl2
R", T_max then " '=Ctrl2 " '; Otherwise, T_max " '=Ctrl2
R";
Wherein said Ctrl1 " ' unit be second; described Ctrl2 " ' unit be second, described TH_n " ' unit be dust; described TH2_n " ' unit be dust, described T_n " unit of ' unit be minute described RR21_n " ' is A/min, described RR21 " ' unit be A/min; described RR20 " unit of ' unit be A/min described Pre1 " ' is dust, described Pre0 " ' unit be dust.
According to method provided by the invention; can in time adjust according to polishing speed, wafer thickness etc. the event horizon of different batches wafer chemically mechanical polishing; thereby more easily monitor out the unusual wafer of polishing time; and can reduce to shut down the frequency of maintenance; increase the validity of monitoring polishing time, increase work efficiency.In addition, inventor's discovery, the method is not only applicable to shallow trench isolation from the chemically mechanical polishing of (STI), also applicable to other chemically mechanical polishings, other CMP techniques such as the polishing of W tungsten film, copper polishing, polishing polycrystalline silicon, aluminium polishing.
The specific embodiment
In the following description, a large amount of concrete details have been provided in order to more thorough understanding of the invention is provided.Yet, it will be apparent to one skilled in the art that the present invention can need not one or more these details and implemented.In other example, for fear of obscuring with the present invention, be not described for technical characterictics more well known in the art.
In order thoroughly to understand the present invention, detailed step will be proposed in following description, in order to being described, the present invention how to realize dynamically adjusting the event horizon of chemically mechanical polishing.Obviously, execution of the present invention is not limited to the specific details that the technical staff of semiconductor applications has the knack of.Preferred embodiment of the present invention is described in detail as follows, yet except these were described in detail, the present invention can also have other embodiments.It should be noted that herein and will when describing embodiment, refer to " chemically mechanical polishing " with " polishing ", so that briefly describe each step and technical term.
The first embodiment
Because the CMP board all will carry out predictive maintenance (Predictivemaintenance, PM) at set intervals, PM weekly for example, PM per month, annual PM.So, if current polished batch wafers after certain predictive maintenance, is then calculated the boundary of the polishing time of this batch wafers with reference to Fig. 1.Otherwise, if current polished batch wafers after certain batch of polished wafer, is then calculated the boundary of the polishing time of this batch wafers with reference to Fig. 2.
Show the method flow diagram that is used for dynamically adjusting according to an embodiment of the invention the chemically mechanical polishing event horizon with reference to Fig. 1, its concrete steps are as follows:
At first, in step 101, respectively to the initial lower limit (Ctrl1 of the polishing time of first batch of polished batch wafers
R, unit is second) and initial higher limit (Ctrl2
R, unit is second) initialize.Wherein, the quantity of described first batch of polished batch wafers is determined according to actual needs, for example, is in one embodiment 25.And the various parameters such as the base material between the different chips in the described first batch of polished batch wafers, polished layer, target polished speed, current wafer thickness, target polished thickness should be unanimous on the whole.Collect the polishing data of all wafers in the particular historical time period (P).Wherein, described special time period is selected according to actual needs, for example 3 months.Described polishing data comprise the actual polishing time of every wafer in this historical time section.Initial lower limit (the Ctrl1 of the polishing time of determining first batch of polished batch wafers according to quantity and the actual polishing time of polished wafer
R, unit is second) and initial higher limit (Ctrl2
R, unit is second).The actual polishing time of some wafers is as the criterion in this time period covering for this initial lower limit and initial higher limit, and this some can for more than 80%, be preferably more than 95%.
Then, in step 102, select the test control wafer of some.This some is at least 4, and for example 4~8, this sentences 4 and is example.
Afterwards, in step 103, on the CMP board, respectively this 4 built-in testing control wafer is polished, calculate the actual polishing speed (RR11_n of every built-in testing control wafer, unit is A/min), then obtain the polishing speed (RR11, unit are A/min) of this BT(batch testing) control wafer.Its determining step is as follows:
A) collect respectively the thickness (TH_Blank1_n, unit be dust) of every built-in testing control wafer before carrying out the CMP polishing;
B) collect respectively the thickness (TH_Blank2_n, unit be dust) of every built-in testing control wafer after finishing the CMP polishing;
C) collect respectively the actual polishing time (T_Blank_n, unit for minute) of every built-in testing control wafer;
D) calculate respectively the actual polishing speed (RR11_n, unit are A/min) of every built-in testing control wafer according to following formula:
RR11_n=(TH_Blank1_n-TH_Blank2_n)/T_Blank_n
Wherein, n=1,2,3,4,
And then calculate the mean value of RR11_n as the polishing speed RR11 of described test control wafer.
Again, in step 104, determine the thickness (Pre1, unit be dust) of first batch of polished batch wafers before carrying out the CMP polishing.Because the parameters such as the thickness of each layer, density, defect distribution, interface state are slightly different, even so for same batch wafers, the thickness of different chips before carrying out the CMP polishing also can be slightly different, therefore average thickness that approx will this first batch of polished batch wafers is considered as Pre1, and its determining step is as follows:
A) wafer of random choose some from first batch of polished batch wafers, the quantity of this first batch of polished batch wafers is preferably 25, and this some is at least 4, and for example 4~6, this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out the CMP polishing;
C) calculate the average thickness of this 4 wafer as the thickness Pre1 of first batch of polished batch wafers before carrying out the CMP polishing.
Then, in step 105, determine in advance that according to actual conditions the target polished speed (RR10, unit for A/min) of test control wafer and first batch of polished batch wafers carrying out the target thickness (Pre0, unit be dust) of CMP before polishing.
Then, in step 106, the model of the reference lower limit value of the first batch of polished batch wafers polishing time of foundation calculating (Ctrl1, unit are second) and reference upper level value (Ctrl2, unit are second) is as follows respectively:
Ctrl1=T1+(RR10-RR11)*K2+(Pre1-Pre0)*K3
Ctrl2=T2+(RR10-RR11)*K2+(Pre1-Pre0)*K3
Wherein, T1, T2 are the values of determining according to actual conditions, and T1 is 40~50s, is preferably 45s, and T2 is 60~70s, is preferably 65s.K2, K3 are weight factor, and K2 was 0.075~0.175 (divides/dust second), are preferably for 0.125 (divide/dust second), and K3 is 0.01~0.03 second/dust, is preferably 0.02 second/dust.They polish data with polissoir, history, production line is relevant.Those skilled in the art can select suitable numerical value according to actual conditions in above-mentioned scope.
At last, in step 107, obtain lower limit (T_min) and the higher limit (T_max) of the polishing time of first batch of polished batch wafers in polishing process according to following mode:
A) if Ctrl1<Ctrl1
R, T_min=Ctrl1 then
R
Otherwise, T_min=Ctrl1;
B) if Ctrl2<Ctrl2
R, T_max=Ctrl2 then;
Otherwise, T_max=Ctrl2
R
If the actual polishing time of the wafer in the first batch of polished batch wafers in the scope of this lower limit and higher limit, illustrates that then the polishing time of this wafer meets the requirements, otherwise illustrates that the polishing time of this wafer is undesirable.
The second embodiment
Show the method flow diagram that is used for dynamically adjusting in accordance with another embodiment of the present invention the chemically mechanical polishing event horizon with reference to Fig. 2, its concrete steps are as follows:
At first, in step 201, respectively to the initial lower limit (Ctrl1 of the polishing time of each polished batch wafers of epicycle
R', unit is second) and initial higher limit (Ctrl2
R', unit is second) initialize.Wherein, the quantity of described each polished batch wafers is determined according to actual needs, for example, is in one embodiment 25.And the various parameters such as the base material between the different chips in described each polished batch wafers, polished layer, target polished speed, current wafer thickness, target polished thickness should be unanimous on the whole.Collect the particular historical time period polishing data of all wafers in (P ').Wherein, described special time period is selected according to actual needs, for example 3 months.Described polishing data comprise the actual polishing time of every wafer in this historical time section.Initial lower limit (the Ctrl1 of the polishing time of determining each polished batch wafers of epicycle according to quantity and the actual polishing time of polished wafer
R', unit is second) and initial higher limit (Ctrl2
R', unit is second).The actual polishing time of some wafers is as the criterion in this time period covering for this initial lower limit and initial higher limit, and this some can for more than 80%, be preferably more than 95%.
Secondly, in step 202, determine last batch wafers polishing speed (RR21 ', unit is A/min) and target polished speed (RR20 ', unit is A/min), and the thickness of current polished batch wafers before carrying out CMP polishing (Pre1 ', unit is dust) and the target thickness before carrying out the CMP polishing (Pre0 ', unit is dust).Wherein:
A) determine the polishing speed (RR21 ', unit is A/min) of last batch wafers, its determining step is as follows:
A) wafer of random choose some in the past one batch wafers, the quantity of this last batch wafers is preferably 25, and this some is at least 4, is preferably 4~6, and this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out CMP polishing (TH1_n ', unit is dust);
C) collect respectively the thickness of every wafer after finishing CMP polishing (TH2_n ', unit is dust);
D) collect respectively every wafer actual polishing time (T_n ', unit for minute);
E) calculate respectively the actual polishing speed (RR21_n ', unit is A/min) of this 4 wafer by following formula:
RR21_n’=(TH1_n’-TH2_n’)/T_n’
Wherein, n=1,2,3,4;
F) calculate the mean value of RR21_n ' as the polishing speed RR21 ' of this last batch wafers.
B) determine the thickness of current polished batch wafers before carrying out CMP polishing (Pre1 ', unit is dust).Because the parameters such as the thickness of each layer, density, defect distribution, interface state are slightly different, even so for same batch wafers, the thickness of different chips before carrying out the CMP polishing also can be slightly different, therefore average thickness that approx will this current polished batch wafers is considered as Pre1 ", its determining step is as follows:
A) wafer of random choose some from current polished batch wafers, the quantity of this current polished batch wafers is preferably 25, and this some is at least 4, and for example 4~6, this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out the CMP polishing;
C) calculate the average thickness of this 4 wafer as the thickness Pre1 ' of current polished batch wafers before carrying out the CMP polishing.
C) according to actual conditions determine in advance last batch wafers target polished speed (RR20 ', unit for A/min) and current polished batch wafers carrying out the target thickness of CMP before polishing (Pre0 ', unit is dust).
In step 203, the model that set up to calculate respectively the reference lower limit value (Ctrl1 ', unit be second) of current polished batch wafers polishing time and reference upper level value (Ctrl2 ', unit is second) is as follows:
Ctrl1’=T3’+(RR20’-RR21’)*K1’+(Pre1’-Pre0’)*K3’
Ctr12’=T4’+(RR20’-RR21’)*K1’+(Pre1’-Pre0’)*K3’
Wherein, T3 ', T4 ' are the values of determining according to actual conditions, and T3 ' is 37~47s, is preferably 42s, and T4 ' is 61~71s, is preferably 66s.K1 ', K3 ' are weight factor, and K1 ' is 0.012~0.032 second minute/dust, are preferably 0.022 second and divide/dust, and K3 ' is 0.01~0.03 second/dust, is preferably 0.02 second/dust.They polish data with polissoir, history, production line is relevant.Those skilled in the art can select suitable numerical value according to actual conditions in above-mentioned scope.
In step 204, obtain the lower limit (T_min ', unit is second) of the polishing time of current polished batch wafers in polishing process and higher limit (T_max ', unit is second) according to following mode:
A) if Ctrl1 '<Ctrl1
R', T_min '=Ctrl1 then
R';
Otherwise, T_min '=Ctrl1 ';
B) if Ctrl2 '<Ctrl2
R', T_max '=Ctrl2 ' then;
Otherwise, T_max '=Ctrl2
R'.
If the actual polishing time of the wafer in the current polished batch wafers in the scope of this lower limit and higher limit, illustrates that then the polishing time of this wafer meets the requirements, otherwise illustrates that the polishing time of this wafer is undesirable.
The 3rd embodiment
Show the method flow diagram that is used for dynamically adjusting the chemically mechanical polishing event horizon of another embodiment according to the present invention with reference to Fig. 3, its concrete steps are as follows:
At first, in step 301, to the initial lower limit (Ctrl1 of the polishing time of each polished batch wafers of epicycle
R", unit is second) and initial higher limit (Ctrl2
R", unit is second) initialize.Wherein, the quantity of described each polished batch wafers is determined according to actual needs, for example, is in one embodiment 25.And the various parameters such as the base material between the different chips in described each polished batch wafers, polished layer, target polished speed, current wafer thickness, target polished thickness should be unanimous on the whole.Collect the particular historical time period polishing data of all wafers in (P ").Wherein, the described particular historical time period is selected according to actual needs, for example 3 months.Described polishing data comprise the actual polishing time of every wafer in this particular historical time period.The initial lower limit of the polishing time of determining each polished batch wafers of epicycle according to quantity and the actual polishing time of polished wafer and initial higher limit.This initial lower limit and initial higher limit with can cover this particular historical in the time period the actual polishing time of some wafers be as the criterion, this some can for more than 80%, be preferably more than 95%.
Then, in step 302, relevant polishing data are polished and collected to the test control wafer.Wherein:
A) select first the test control wafer of some.This some is at least 4, and for example 4~8, this sentences 4 and is example.
B) on the CMP board, respectively this 4 built-in testing control wafer is polished, determine every built-in testing control wafer actual polishing speed (RR11_n "; unit is A/min), then obtain the polishing speed (RR11 ", unit is A/min) of this BT(batch testing) control wafer.Its determining step is as follows:
A) collect respectively the thickness of every built-in testing control wafer before carrying out CMP polishing (TH_Blank1_n ", unit is dust);
B) collect respectively the thickness of every built-in testing control wafer after finishing CMP polishing (TH_Blank2_n ", unit is dust);
C) collect respectively every built-in testing control wafer actual polishing time (T_Blank_n ", unit for minute);
D) calculate respectively the actual polishing speed (RR11_n ", unit is A/min) of every built-in testing control wafer according to following formula:
RR11_n”=(TH_Blank1_n”-TH_Blank2_n”)/T_Blank_n”
Wherein, n=1,2,3,4,
And then calculate RR11_n " mean value as the polishing speed RR11 of described test control wafer ".
C) determine the thickness of first batch of polished batch wafers before carrying out CMP polishing (Pre1 ", unit is dust).Because the parameters such as the thickness of each layer, density, defect distribution, interface state are slightly different, even so for same batch wafers, the thickness of different chips before carrying out the CMP polishing also can be slightly different, therefore average thickness that approx will this first batch of polished batch wafers is considered as Pre1 ", its determining step is as follows:
A) wafer of random choose some from this first batch of polished batch wafers, the quantity of this first batch of polished batch wafers is preferably 25, and this some is at least 4, and for example 4~6, this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out the CMP polishing;
C) calculate the average thickness of this 4 wafer as the thickness Pre1 of this first batch of polished batch wafers before carrying out the CMP polishing ".
D) according to actual conditions determine in advance the test control wafer target polished speed (RR10 ", unit for A/min) and this first batch of polished batch wafers carrying out the target thickness of CMP before polishing (Pre0 ", unit is dust).
Afterwards, in step 303, the model that set up to calculate respectively the reference lower limit value (Ctrl1 ", unit be second) of first batch of polished batch wafers polishing time and reference upper level value (Ctrl2 ", unit is second) is as follows:
Ctrl1”=T1”+(RR10”-RR11”)*K2”+(Pre1”-Pre0”)*K3”
Ctrl2”=T2”+(RR10”-RR11”)*K2”+(Pre1”-Pre0”)*K3”
Wherein, T1 ", T2 " be the value of determining according to actual conditions, T1 " be 40~50s, be preferably 45s, T2 " be 60~70s, be preferably 65s.K2 ", K3 " be weight factor, K2 " be 0.075~0.175 (second minute/dust), be preferably 0.125 (second minute/dust), K3 " be 0.01~0.03 second/dust, be preferably 0.02 second/dust.They polish data with polissoir, history, production line is relevant.Those skilled in the art can select suitable numerical value according to actual conditions in above-mentioned scope.
Subsequently, in step 304, obtain the lower limit (T_min ", unit is second) of the polishing time of first batch of polished batch wafers in polishing process and higher limit (T_max ", unit is second) according to following mode:
If a) Ctrl1 "<Ctrl1
R", T_min then "=Ctrl1
R";
Otherwise, T_min "=Ctrl1 ";
B) if Ctrl2 "<Ctrl2
R", T_max then "=Ctrl2 ";
Otherwise, T_max "=Ctrl2
R".
If the actual polishing time of the wafer in this first batch of batch wafers in the scope of this lower limit and higher limit, illustrates that then the polishing time of this wafer meets the requirements, otherwise illustrates that the polishing time of this wafer is undesirable.
Next, in step 305, for second batch and follow-up each batch wafers, determine last batch wafers actual polishing speed (RR21 " '; unit is A/min) and target polished speed (RR20 " ', unit is A/min), and the thickness of current polished batch wafers before carrying out the CMP polishing (Pre " '; unit is dust) and the target thickness before carrying out the CMP polishing (Pre0 " ', unit is dust).Wherein:
A) determine the actual polishing speed (RR21 " ', unit is A/min) of last batch wafers, its determining step is as follows:
A) wafer of random choose some in the past one batch wafers, the quantity of this last batch wafers is preferably 25, and this some is at least 4, is preferably 4~6, and this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out CMP polishing (TH1_n " ', unit is dust);
C) collect respectively the thickness of every wafer after finishing CMP polishing (TH2_n " ', unit is dust);
D) collect respectively every wafer actual polishing time (T_n " ', unit for minute);
E) calculate respectively the actual polishing speed (RR11_n " ', unit is A/min) of every wafer according to following formula:
RR21_n”’=(TH1_n”’-TH2_n”’)/T_n”’
Wherein, n=1,2,3,4;
F) calculate RR21_n " ' mean value as the polishing speed RR21 of this last batch wafers " '.
B) determine the thickness of current polished batch wafers before carrying out CMP polishing (Pre1 " ', unit is dust).Because the parameters such as the thickness of each layer, density, defect distribution, interface state are slightly different, even so for same batch wafers, the thickness of different chips before carrying out the CMP polishing also can be slightly different, therefore average thickness that approx will this polished batch wafers is considered as Pre1 ", its determining step is as follows:
A) wafer of random choose some from current polished batch wafers, the quantity of this current polished batch wafers is preferably 25, and this some is at least 4, and for example 4~6, this sentences 4 and is example;
B) collect respectively the thickness of every wafer before carrying out the CMP polishing;
C) calculate the average thickness of this 4 wafer as the thickness Pre1 of current polished batch wafers before carrying out the CMP polishing " '.
C) according to actual conditions collect in advance last batch wafers target polished speed (RR20 " ', unit for A/min) and current polished batch wafers carrying out the target thickness of CMP before polishing (Pre0 " ', unit is dust).
In step 306, the model that set up to calculate respectively the reference lower limit value (Ctrl1 " ', unit be second) of current polished batch wafers polishing time and reference upper level value (Ctrl2 " ', unit is second) is as follows:
Ctrl1”’=T3”’+(RR20”’-RR21”’)*K1”’+(Pre1”’-Pre0”’)*K3”’
Ctrl2”’=T4”’+(RR20”’-RR21”’)*K1”’+(Pre1”’-Pre0”’)*K3”’
Wherein, T3 " ', T4 " ' be the value of determining according to actual conditions, T3 " ' be 37~47s, be preferably 42s, T4 " ' be 61~71s, be preferably 66s.K1 " ', K3 " ' be weight factor, K1 " ' be 0.012~0.032 second minute/dust, be preferably 0.022 second minute/dust, K3 " ' be 0.01~0.03 second/dust, be preferably 0.02 second/dust.They polish data with polissoir, history, production line is relevant.Those skilled in the art can select suitable numerical value according to actual conditions in above-mentioned scope.
In step 307, set up judgment formula, obtain the lower limit (T_min ", unit is second) of the polishing time of current polished batch wafers in polishing process and higher limit (T_max ", unit is second):
If a) Ctrl1 " '<Ctrl1
R", T_min=Ctrl1 then
R";
Otherwise, T_min " '=Ctrl1 " ';
B) if Ctrl2 " '<Ctrl2
R", T_max then " '=Ctrl2 " ';
Otherwise, T_max " '=Ctrl2
R".
If the actual polishing time of the wafer in the current polished batch wafers in the scope of this lower limit and higher limit, illustrates that then the polishing time of this wafer meets the requirements, otherwise illustrates that the polishing time of this wafer is undesirable.
In addition, because the CMP board all will carry out predictive maintenance (Predictivemaintenance, i.e. PM) at set intervals, such as PM weekly, PM per month, annual PM.So; if current polished batch wafers is after certain predictive maintenance; perhaps long-time the shutdown appears in CMP equipment; all need to treat before polished wafer carries out glossing; the test control wafer is polished, with lower limit and the higher limit of the polishing time of determining current polished batch wafers.That is, behind completing steps 310, if CMP equipment has carried out predictive maintenance or long-time shutdown occurred, the polished wafer of next batch need to re-start step 302 so.Otherwise, carry out step 305.
In each embodiment of the present invention, to utilize the Reflection polissoir of company of Applied Materials (AMAT) to treat polished wafer and polish, its polishing pad model is IC1010.The test control wafer is for through after the high density plasma CVD oxide layer, without the wafer of any pattern.Polished batch wafers for through after the high density plasma CVD oxide layer, be with figuratum wafer.Table 1A and 1B show respectively the value condition of each parameter among the first two embodiment of the present invention and polishing time lower limit that the method according to this invention calculates and the example of higher limit.
T1 |
45 seconds |
T2 |
65 seconds |
RR11 |
1350 A/mins |
RR10 |
1300 A/mins |
Pre1 |
5539 dusts |
Pre0 |
5500 dusts |
K2 |
0.125 divide/dust second |
K3 |
0.02 second/dust |
Ctrl1 |
39.5 second |
Ctrl2 |
59.5 second |
Table 1A
T3’ |
42 seconds |
T4’ |
66 seconds |
RR21’ |
2471.4 A/min |
RR20’ |
2400 A/mins |
Pre1’ |
5539 dusts |
Pre0’ |
5500 dusts |
K1’ |
0.022 divide/dust second |
K3’ |
0.02 second/dust |
Ctrl1’ |
41.2 second |
Ctrl2’ |
65.2 second |
Table 1B
The present invention is illustrated by above-described embodiment, but should be understood that, above-described embodiment just is used for for example and the purpose of explanation, but not is intended to the present invention is limited in the described scope of embodiments.It will be appreciated by persons skilled in the art that in addition the present invention is not limited to above-described embodiment, can also make more kinds of variants and modifications according to instruction of the present invention, these variants and modifications all drop in the present invention's scope required for protection.Protection scope of the present invention is defined by the appended claims and equivalent scope thereof.