A kind of chip failure analytical approach
Technical field
The present invention relates to the semiconductor failure analysis field, particularly a kind of chip failure analytical approach.
Background technology
In the modern integrated circuits manufacturing process, chip manufacture need experience process procedures such as a series of chemistry, optics, metallurgy, hot-working.Per pass technology all may be introduced various defectives.Meanwhile because constantly the dwindling of characteristic dimension, all kinds of processing facility costs also sharply rise, so the loss cost that device defects causes is very high.Under this condition, by validation test, analyze failure cause, reduce device defects and just become indispensable link in the integrated circuit manufacturing.By failure analysis work, can help the integrated circuit (IC) design personnel to find not matching of defective in the design, technological parameter, also help integrated circuit application personnel to find to use problems such as design or misoperation simultaneously.
The failure analysis common method has a lot, roughly is divided into two kinds of hard method (Hard Method) and soft methods (SoftMethod).Hard method comprises that mainly hardware devices such as using photoelectric microscope checks and definite failure cause, thereby improves technological process.At present, these are used to diagnose, the system and the advanced analytical equipment instrument of failure analysis comprise electron beam probe (E-beam probe) diagnostic system, plasma beam mending system (FIB-Focused Ion Beam), thermal infrared imager, scanning electron microscope (SEM-Scanning ElectronMicroscopy), Laser Scanning Confocal Microscope, analyzing parameters of semiconductor instrument etc.The failure analysis personnel just can analyze each top layer of chip and longitudinal profile by using these instruments, and accurately the positioning chip defective provides complete failure analysis report.
In the present prior art, the chip failure analytical approach adopts the method for cmp that chip is successively peeled off usually and then adopts above-mentioned hard method to check and whether definite chip lost efficacy.With non-volatile Flash memory chip is example, be illustrated in figure 1 as the side structure cut-open view of Flash memory chip, this chip comprises substrate 1, has active area 2 (source-drain area) in the substrate 1, be formed with grid oxide layer 3, control grid 4 and metal level 5 on the substrate 1 successively, wherein, grid oxide layer 3 is the stepped construction of monox, silicon nitride, monox, be the ONO structure, silicon nitride is used for stored charge; Grid 4 is made of first polysilicon layer 41 and second polysilicon layer 42; Metal level 5 can be provided with one or more layers according to cabling requirement, as signal, has drawn three layers among the figure.Because the bottom live width of grid 4 is for the reading and writing of Flash storer and wipe the performance important influence, therefore, failure analysis at this Flash memory chip mainly passes through to measure grid 4 bottom sizes, the i.e. length and wide the carrying out of first polysilicon layer, 41 bottoms, after the bottom size that obtains first polysilicon layer 41, again by observing and relatively judging whether this grid exists the defect characteristic that causes chip failure.
Owing to also be coated with grid second polysilicon layer 42 and metal level 5 on first polysilicon layer 41, for the bottom that can directly observe grid first polysilicon layer 41 and then measure its characteristic dimension, in the prior art, usually successively stripping metal layer 5, grid second polysilicon layer 42, grid first polysilicon layer 41 adopt scanning electron microscope sem or perspective Electronic Speculum TEM to check the bottom length and width equidimension of grid first polysilicon layer 41 until the bottom of exposing first polysilicon layer 41 then from chip front side to adopt chemical mechanical milling method.But in fact, adopt the method to grind when peeling off grid first polysilicon layer 41 to be the bottom that is difficult to peel off accurately stop to the first polysilicon layer 41, operating personnel are ground to the grid oxide layer 3 or the active area 2 of chip through regular meeting.Even grind the zone that has finally rested on very close first polysilicon layer, 41 bottoms, because factors such as abrasion error or uneven thickness, the size of first polysilicon layer, 41 bottoms that finally record also is easy to generate error, so just be easy to deal with problems and cause misleading, and general about 10 first polysilicon layer, 41 bottom sizes of every observation just need 4 hours to the slip-stick artist.This shows that the method efficient that prior art adopts is very low, success ratio is very little, and the data that obtain are also inaccurate.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of chip failure analytical approach, and very difficult precisely grinding efficiently is stripped to the bottom of grid ground floor polysilicon to record the problem of its bottom accurate size parameter in the failure analysis of chip to solve.
For solving the problems of the technologies described above, the invention provides a kind of chip failure analytical approach, be used to detect the defect characteristic that causes chip failure, may further comprise the steps:
Remove the substrate of the chip that carries out failure analysis and the major part of active area by mechanical lapping;
Remove remaining substrate and the active area of chip by wet etching;
Remove the major part of the grid oxide layer of chip by dry etching, the part grid oxide layer of reservation is used to protect grid first polysilicon layer;
Detect described first polycrystal layer and whether have defect characteristic.
Optionally, the step of described chip failure analytical approach also comprises: the chip front side that will carry out failure analysis before carrying out mechanical lapping pastes on the plummer with bonding agent down.
Optionally, the described chip that carries out failure analysis can be a complete chip, also can be the part of the chip under the cutting.
Optionally, the material of described plummer is a glass.
Optionally, described mechanical lapping can automatically be ground and realizes by plummer and chip being put into automatic grinding device.
Optionally, the manual plummer of lifting of described mechanical lapping employing is pressed in sample the mechanical lapping that realizes on the muller chip.
Optionally, describedly remove the remaining substrate of chip and the step of active area comprises by wet etching: chip is together put into together with plummer in the weakly alkaline solution of the heating that has added isopropyl alcohol, and remaining substrate and active area removed fully on chip.
Optionally, the temperature of the weakly alkaline solution of described heating is 80-85 ℃.
Optionally, described weakly alkaline solution is that concentration is lower than 40% potassium hydroxide solution.
Optionally, described wet etching is removed the remaining substrate of chip and the step of active area also comprises: pull out after chip is put into hydrogen peroxide number minute together with plummer, use deionized water chip to be cleaned and make the chip drying.
Optionally, the temperature of described hydrogen peroxide is 50-90 ℃.
Optionally, adopt high vacuum scanning electron microscope or low vacuum scanning electron microscope to detect described first polycrystal layer and whether have defect characteristic.Preferred low vacuum scanning electron microscope.
Chip failure analytical approach provided by the invention can accurately be peeled off chip to the bottom of grid ground floor polysilicon, record the accurate dimension parameter of its bottom, and skilled operating personnel adopt method of the present invention to carry out the bottom size of all grid ground floor polysilicons can be just finished in failure analysis within 2 hours observation, improve work efficiency greatly, saved time cost.
Description of drawings
Fig. 1 is the side structure cut-open view of Flash memory chip;
Fig. 2 a-Fig. 2 d is a chip failure analytical approach step synoptic diagram of the present invention;
Fig. 3 is the process flow diagram of chip failure analytical approach 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.
Chip failure analytical approach of the present invention can be widely used in the failure analysis of memory chip and other semi-conductor chips; and can utilize multiple substitute mode to realize; be to be illustrated below by preferred embodiment; certainly the present invention is not limited to this specific embodiment, and the known general replacement of one of ordinary skilled in the art is encompassed in protection scope of the present invention far and away.
Secondly, the present invention utilizes synoptic diagram to describe in detail, and when the embodiment of the invention was described in detail in detail, for convenience of explanation, synoptic diagram was disobeyed the local amplification of general ratio, should be with this as limitation of the invention.
Below be that example describes the inventive method in detail with the failure analysis of Flash memory chip.
Please at first consult Fig. 1, Figure 1 shows that the side structure cut-open view of Flash memory chip.As shown in Figure 1, the structure of chip comprises substrate 1 as describing in detail in background technology, have active area 2 (source-drain area) in the substrate 1, be formed with grid oxide layer 3, control grid 4 and metal level 5 on the substrate 1 successively, wherein grid 4 is made of first polysilicon layer 41 and second polysilicon layer 42.Because ground floor polysilicon 41 oxide-semiconductor control transistors of grid, operation such as affect the reading and writing of chip and wipe, the length and width size of its bottom has determined that the grid of active device are long, and can influence transistorized performance, thereby the length and width size of its bottom has become the important dimensional parameters of product.Therefore, at the grid progress row failure analysis of chip the time, need to measure the length and width dimensional parameters of ground floor polysilicon 41 bottoms of grid.Common metal level 5 in the prior art from chip front side, successively peel off the second layer polysilicon 42 of grid, the ground floor polysilicon 41 of grid by mechanical lapping, until the bottom of the ground floor polysilicon 41 that exposes grid and then measure its length and width size, chip failure analytical approach of the present invention is then from the back side substrate 1 of chip, method by mechanical lapping and etching phase combination can finally intactly reveal ground floor polysilicon 41 bottoms of grid, and then records its length and width dimensional data accurately.
Describe chip failure analytical approach of the present invention in detail below in conjunction with Fig. 2 a-Fig. 2 d and Fig. 3.Fig. 2 a-Fig. 2 d is a chip failure analytical approach step synoptic diagram of the present invention, and Fig. 3 is the process flow diagram of chip failure analytical approach of the present invention.Chip structure among Fig. 2 a-Fig. 2 d is identical with the chip structure of Fig. 1, and Yin Ben second layer polysilicon 2 of metal level 1 and grid in inventive method does not need to mention so it is not marked in the chip structure of Fig. 2 a-2d.
At first, shown in Fig. 2 a, the metal level of need being carried out the chip of failure analysis pastes on the plummer 9 with bonding agent 8 down.
The chip that adopts the inventive method to carry out failure analysis can be a complete chip, also can be the part of the chip under the cutting; Plummer 9 can be the material of glass or other quality; The adhesion of bonding agent 8 must be finished ensuing mechanical lapping and heat treatment process by supporting chip on plummer 9.
Secondly, shown in Fig. 2 a and Fig. 2 b, remove the substrate 1 of chip and the major part of active area 2 by mechanical lapping.
Begin the substrate 1 and the active area 2 of chip are carried out mechanical lapping from the back of chip, until the major part that peels off substrate 1 and active area 2, almost imperceptible chip or can stop to grind during printing opacity when chip when stroking the edge of plummer 9 with hand.Above-mentioned process of lapping can adopt to be put into the mode that automatic grinding device automatically grinds with plummer 9 and chip and realizes, also can adopt the manual plummer of lifting sample is pressed in the mode that realizes on the muller the mechanical lapping of chip realizes.
Once more, shown in Fig. 2 b and Fig. 2 c, remove remaining substrate 1 and the active area 2 of chip by wet etching.
The chip that will pass through mechanical lapping was together put into together with plummer 9 in the weakly alkaline solution of the heating that has added isopropyl alcohol several minutes, until shown in Fig. 2 c with chip on by mechanical lapping after remaining substrate 1 and active area 2 remove fully; The temperature of the weakly alkaline solution of described heating is 80-85 ℃; Be a kind of embodiment of the present invention, described weakly alkaline solution can be concentration and is lower than 40% potassium hydroxide solution.Chip together with plummer 9 put in hydrogen peroxide and pull out after several minutes, use deionized water chip to be cleaned and make the chip drying thereafter; The temperature of described hydrogen peroxide can be chosen between 50-90 ℃.
Once more, shown in Fig. 2 c and Fig. 2 d, remove the major part of the grid oxide layer 3 of chip, keep the integrality of grid oxide layer 3 oxides of skim with protection grid ground floor polysilicon 41 bottoms by dry etching.
So far, the bottom characteristic of the grid ground floor polysilicon 41 of chip comes out.
At last, utilize the length and width dimensional parameters of chip grid ground floor polysilicon 41 bottoms on the observation instrument observation plummer 9.
Observation instrument can adopt high vacuum scanning electron microscope (High Vacuum SEM) or low vacuum scanning electron microscope (Low Vacuum SEM), because it is extremely thin through mechanical lapping and chip after etching, can not well meet the observation requirement of high vacuum scanning electron microscope, thereby adopt the low vacuum scanning electron microscope to be observed the preferred version of the inventive method.
Above method is a kind of embodiment of the inventive method at a kind of chip structure, and the inventive method can be widely used in the failure analysis of different memory chip and other semi-conductor chips.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.