Embodiment
From background technology, by the be etched optical emitting of the contained element of rete of monitoring, compose the method for the etching terminal of monitoring plasma body etching technics can not monitor exactly etching terminal.Inventor studies for the problems referred to above, finds that prior art normally obtains by optical emission spectroscopy the luminous intensity of element and the curve of time that collection detects, and waits until that the luminous intensity of described element starts to reduce, and is etching terminal.
But, limitation due to existing equipment, while adopting measuring equipment to measure the luminous intensity of element and the curve of time, there is certain time of delay the time that the time starting most of the curve obtaining and measuring equipment start to measure, therefore, be defined as the time of delay of etching: while conventionally starting etching, the reactant in plasma igniting rear chamber and production concentration have a stable process, therefore before detection etch terminal, set a time of delay (delay time).If select improper time of delay, can affect the detection of etching terminal, even can't detect etching terminal.
In the method for measurement of prior art, the method for supervising of the etching terminal of existing judgement plasma etch process judges the time of delay of etching terminal conventionally by operating personnel's experience, make the etching terminal of plasma etch process inaccurate, affect the accuracy of etching.
For this reason, the present inventor proposes a kind of etching terminal dynamic testing method of optimization, solve the defect that prior art is ignored the time of delay of etching terminal or judged the time of delay of etching terminal by operating personnel's experience, please refer to Fig. 1, comprise the steps:
Step S101, obtain the intensity that starts the Real-Time Optical signal that completes to etching from etching, wherein, from etching, start to complete to etching and comprise section time of delay, stablize etch period section and the etching terminal judgement time period, the intensity of described specific wavelength light signal is corresponding with specific etching gas active component concentration or production concentration in etching cavity;
Step S102, provides default section reference threshold time of delay;
Step S103, the flex point of the Real-Time Optical signal strength signal intensity of search delay in the time period, if search flex point in described time of delay in section, enters and stablizes etch period section, if without flex point, enter and stablize etch period section after arriving reference threshold in described default time of delay section.
Embodiments of the invention are by obtaining the intensity curve that starts the Real-Time Optical signal that completes to etching from etching, and inventor finds in respective intensities curve, to have flex point time of delay, thereby can accurately judge time of delay.
Below in conjunction with a specific embodiment, etching terminal dynamic testing method of the present invention is described in detail.
Execution step S101, obtain the intensity that starts the Real-Time Optical signal that completes to etching from etching, wherein, from etching, start to complete to etching and comprise section time of delay, stablize etch period section and the etching terminal judgement time period, the intensity of described specific wavelength light signal is corresponding with specific etching gas active component concentration or production concentration in etching cavity.
In one embodiment, obtaining the intensity curve that starts the Real-Time Optical signal that completes to etching from etching specifically comprises:
One etching apparatus is provided, and described etching apparatus is plasma etching equipment, and described etching apparatus has etching cavity, and chip to be etched is placed on the carrier of described cavity;
In etching cavity, pass into etching gas, using plasma etching apparatus carries out etching to described chip to be etched;
By being arranged on detector in described plasma etching equipment, gather the light signal in etching cavity, described light signal refer to the different wave length that in etching cavity, etching reactant and etching product are launched light in each intensity constantly;
In one embodiment, when with fluorocarbon gas etching oxidation silicon, in the accessory substance that etching produces, have CO, its corresponding spectral wavelength is 483nm, passes through the peak intensity of detection 483nm over time, just can know the variation of CO concentration in cavity; Thereby infer SiO
2situation about being etched.
In another embodiment, when with fluorocarbon gas etching SiN (silicon nitride), accessory substance is CN, and its corresponding spectral wavelength is 387nm, passes through the peak intensity of detection 387nm over time, just can know the variation of CN concentration in cavity; Thereby infer the situation that SiN is etched.
It should be noted that; when the selection of the type of chip to be etched and the type of etching gas different; described specific wavelength light signal also can corresponding difference; but; the intensity of described specific wavelength light signal is corresponding with specific etching gas active component concentration or production concentration in etching cavity; those skilled in the art can be according to the type of the type of etching chip and etching gas; select corresponding specific wavelength light signal; and obtain the intensity of described specific wavelength light signal; at this, specially illustrate, should too not limit the scope of the invention.
Also it is to be noted; limitation due to equipment; while adopting measuring equipment to measure the luminous intensity of element and the curve of time; there is certain time of delay the time that the time starting most of the curve obtaining and measuring equipment start to measure; in the method for measurement of prior art; the method for supervising of the etching terminal of existing judgement plasma etch process can be ignored the time of delay of etching terminal conventionally; or by operating personnel's experience, judge the time of delay of etching terminal; make the etching terminal of plasma etch process inaccurate, affect the accuracy of etching.
For this reason, embodiments of the invention are after execution of step S101, and execution step S102, provides default section reference threshold time of delay.
Reference threshold was positioned at described reference threshold time time of delay for judgement and whether had flex point described time of delay, described time of delay, reference threshold can be by multiple etching chip to be etched under identical conditions, and the over etching degree of testing chip to be etched obtains, also can obtain from etching starts the intensity curve of the Real-Time Optical signal that completes to etching by identical conditions, the slightly long time of the time of delay of directly experience being obtained is set as described time of delay of reference threshold.
In one embodiment, described time of delay, section reference threshold was empirical value, described time of delay, section reference threshold was less than 10 seconds, such as described time of delay section reference threshold be 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds or 9 seconds, preferably, described time of delay, section reference threshold was 5 seconds or 6 seconds.
In one embodiment, described time of delay, reference threshold preparation method was:
The intensity curve that starts the Real-Time Optical signal that completes to etching from etching is provided, and the intensity curve acquisition methods of the Real-Time Optical signal that the intensity curve of described Real-Time Optical signal can refer step S101, here repeats no more.
Adjacent sampling time interval is provided, within the time of a times of adjacent time in sampling interval, a is more than or equal to 1 natural number, the slope absolute value maximum in the relative sampling time of intensity of search Real-Time Optical signal, and the difference DELTA I of the intensity that obtains light signal corresponding to slope absolute value maximum and light signal strength with previous time point, in the scope of 0 to a Δ I, choose reference value B;
To I
n-a+ B and I
nvalue compare, when:
Curve is ascending curve, and I
n-a+ B > I
n, I
nthe corresponding time is reference threshold time of delay;
Curve is decline curve, and I
n-a-B < I
n, I
nthe corresponding time is reference threshold time of delay;
Wherein, I
n-abe the intensity of n-a Real-Time Optical signal, I
nbe the intensity of n Real-Time Optical signal, n is natural number.
Wherein, the determination methods of ascending curve is: choose P continuous time period, P is greater than 1, and gathers the etching signal of each time period terminal, is designated as successively I
1, I
2... I
n, I
n+1... I
pif selected P etching signal value increases successively, judge in the described time period to be ascending curve.
The determination methods of decline curve is: choose Q continuous time period, Q is greater than 1, and gathers the etching signal of each time period terminal, is designated as successively I
1, I
2... I
n, I
n+1... I
qif selected Q etching signal value declines successively, judge in the described time period to be decline curve.
Particularly, total duration of P time period and the duration of each time period can be selected according to signal to noise ratio of etching technics, etching signal etc.With reference to figure 2, Fig. 2 is the variation relation schematic diagram of the etching signal intensity time of an embodiment, wherein the longitudinal axis is etching signal intensity, transverse axis is the time, in the present embodiment, the corresponding duration P ' of rising edge of the crest of etching signal that can be per sample, total duration of a selected P time period while selecting the etching terminal of sample of same batch of monitor subsequent.Total duration of P time period can be greater than or equal to P '.
The numerical value of P also can be selected according to concrete technique, or take Fig. 2 as example, in Fig. 2, represent in the more rough situation of curve of etching signal, in the situation that total duration of P time period is definite, the numerical value of described P can be smaller, to avoid a little overstocked because of getting, and be subject to the interference of the noise in signal, and can be according to the situation of noise, the terminal of each time period of P time period described in reasonable distribution, such as, every 0.01s, there is a noise waves, the integral multiple that the length that can be each time period of P time period is 0.01s.Preferably, a described P time period is isometric, the isometric accuracy that can improve rising edge judgement of a described P time period, and noise decrease disturbs.
As shown in Figure 3, searching I
1, I
2... I
n, I
n+1... I
pafter the etching signal that P increases successively altogether, search rising edge.
In another embodiment, start in etching signal, to search for trailing edge, the search procedure of described trailing edge comprises: choose Q continuous time period, Q is greater than 1, and gathers the etching signal of each time period terminal, is designated as successively I
i+1, I
i+2... I
i+n, I
i+n+1... I
i+Qif selected Q etching signal value declines successively, obtains the trailing edge of described etching signal; If I
i+nbe less than or equal to I
i+n+1, from I
i+n+1start again to choose Q continuous time period, gathers and compare the etching signal of each time period terminal, until obtain the individual etching signal reducing successively of Q, think and obtain the trailing edge of etching signal.
Particularly, total duration of Q time period and the duration of each time period can be selected according to signal to noise ratio of etching technics, etching signal etc.With reference to figure 4, the intensity that in Fig. 4, the longitudinal axis is etching signal, transverse axis is the time, in the present embodiment, the corresponding duration Q ' of the trailing edge of the crest of etching signal that can be per sample selects total duration of Q time period.Total duration of a described Q time period can be greater than or equal to Q '.
The numerical value of Q also can be selected according to concrete technique, or take Fig. 4 as example, in Fig. 4, represent in the more rough situation of curve of etching signal, in the situation that total duration of Q time period is definite, the numerical value of described Q can be smaller, to avoid a little overstocked because of getting, and be subject to the interference of the noise in signal, and can be according to the situation of noise, the terminal of each time period of Q time period described in reasonable distribution, such as, every 0.02s, there is a noise waves, the integral multiple that the length that can be each time period of Q time period is 0.02s.Preferably, a described Q time period is isometric, the isometric accuracy that can improve trailing edge judgement of a described Q time period, and noise decrease disturbs.
As shown in Figure 5, searching I
i+1, I
i+2... I
i+n, I
i+n+1... I
i+Qafter the etching signal that Q declines successively continuously, search trailing edge.
Execution step S103, the flex point of the Real-Time Optical signal strength signal intensity of search delay in the time period, if search flex point in described time of delay in section, enters and stablizes etch period section, if without flex point, enter and stablize etch period section after arriving reference threshold in described default time of delay section.
Inventor finds: in time of delay section, a light intensity for material in etch chamber can continue to change, but at terminal time of delay, the rate of change of sending out light intensity of the material in described etch chamber has a flex point, please refer to Fig. 6, when Fig. 6 is etching oxidation silicon, the change curve of the wavelength 483nm spectrum peak intensity time that accessory substance CO that etching produces is corresponding, in the embodiment of etching oxidation silicon, before adopting, step arranges described time of delay of reference threshold, and the flex point of the relative etch period of intensity of the Real-Time Optical signal in described time of delay reference threshold, obtain time of delay.
Particularly, the flex point of the Real-Time Optical signal strength signal intensity in described time of delay of section can obtain by following manner:
Mode 1:
The determination methods of described flex point is: the intensity of search specific wavelength Real-Time Optical signal and the slope of time, the intensity curve slope of Real-Time Optical signal is that the point of 0 correspondence is flex point.
The intensity curve of Real-Time Optical signal of etching oxidation silicon of Fig. 6 of take is example, transverse axis is detection time, the longitudinal axis is the intensity of Real-Time Optical signal, the intensity curve of the Real-Time Optical signal of described etching oxidation silicon is tried to achieve to the slope of 483nm spectrum peak intensity and time, the point that is 0 correspondence when 483nm spectrum peak intensity curve slope is flex point, and time corresponding to flex point is time of delay.
Mode 2:
The determination methods of described flex point is: the optical signal noise signal strength signal intensity when obtaining plasma etching and stablizing, arranges Δ I=I
n-I
n-1, during optical signal noise signal strength signal intensity when if absolute value < 10 * plasma etching of Δ I is stablized, I
ncorresponding time point is flex point, wherein, and I
nbe the intensity of n Real-Time Optical signal, I
n-1be the intensity of n-1 Real-Time Optical signal, n is greater than 1 natural number.
Please refer to Fig. 7, Fig. 7 is the intensity curve of etching SiN (silicon nitride) Real-Time Optical signal, and transverse axis is detection time, the longitudinal axis is the intensity of Real-Time Optical signal, accessory substance is CN, and the spectral wavelength that CN is corresponding is 387nm, in the intensity curve of etching SiN Real-Time Optical signal, Δ I=I is set
n-I
n-1, during optical signal noise signal strength signal intensity when the absolute value < of Δ I 10 * plasma etching is stablized, I
ncorresponding time point is flex point, wherein, and I
nbe the intensity of n Real-Time Optical signal, I
n-1be the intensity of n-1 Real-Time Optical signal, n is greater than 1 natural number.
Mode 3
Provide adjacent sampling time interval, the difference DELTA In=I of the intensity of light signal and the light signal strength of previous time point
n-I
n-1, when Δ In be greater than Δ In-1 numerical value 80% time enter and stablize etch period section, wherein I
nbe the intensity of n Real-Time Optical signal, wherein, I
n-1be the intensity of n-1 Real-Time Optical signal, n is greater than 1 natural number.
Also it should be noted that, in other embodiments, the flex point of the relative etch period of intensity of the Real-Time Optical signal in time of delay reference threshold can for a plurality of, for example, be: 2,3,4 ....; In this embodiment, the time of delay that etch period corresponding to first flex point searching is corresponding etching; If, without flex point, time of delay, reference threshold was defined as time of delay of etching in described time of delay reference threshold.
Preferably, in order to reduce the erroneous judgement of the flex point causing because of interference such as signal noises, break, occur, after first flex point, occurring continuously a plurality of flex points in time of delay in reference threshold, selecting the time corresponding to flex point of first appearance is time of delay; Such as, after there is first flex point, each point in there are 10 seconds of first flex point meets the requirement of flex point.
It should be noted that, if described time of delay, section internal reference threshold value existed flex point, enter and stablize etch period section; If without flex point, enter and stablize etch period section after arriving reference threshold in described default time of delay section.
After step in, section time of delay that can adopt each embodiment of the present invention to obtain by input, thereby adopt variety of way to carry out the etching terminal of monitoring plasma body etching technics, the acquisition pattern of the etching terminal of plasma etch process can, with reference to the etching terminal judgment mode of existing plasma etch process, here repeat no more particularly.
Embodiments of the invention are by the flex point of the relative etch period of intensity of the Real-Time Optical signal in search delay time reference threshold value, obtain accurate time of delay, avoid judging by operating personnel's experience the defect of the time of delay of etching terminal, thereby can overcome the limitation of etching apparatus, adopt that embodiments of the invention obtain time of delay monitoring plasma body etching technics etching terminal accuracy high.
Although the present invention with preferred embodiment openly as above; but it is not for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can utilize method and the technology contents of above-mentioned announcement to make possible change and modification to technical solution of the present invention; therefore; every content that does not depart from technical solution of the present invention; any simple modification, equivalent variations and the modification above embodiment done according to technical spirit of the present invention, all belong to the protection range of technical solution of the present invention.