CN213212113U - Wafer life test equipment - Google Patents
Wafer life test equipment Download PDFInfo
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- CN213212113U CN213212113U CN202022530874.1U CN202022530874U CN213212113U CN 213212113 U CN213212113 U CN 213212113U CN 202022530874 U CN202022530874 U CN 202022530874U CN 213212113 U CN213212113 U CN 213212113U
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- 238000012360 testing method Methods 0.000 title claims abstract description 101
- 238000001514 detection method Methods 0.000 claims abstract description 38
- 230000003647 oxidation Effects 0.000 claims abstract description 22
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- 239000000523 sample Substances 0.000 claims description 38
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
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- 239000001301 oxygen Substances 0.000 claims description 17
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Abstract
The utility model provides a wafer life-span test equipment, include: a placing device for placing the wafer; the oxidation device is used for oxidizing the surfaces of the two sides of the wafer; the detection device is used for sequentially passivating the surfaces of two sides of the oxidized wafer and testing the service life of a current carrier on the surface of one passivated wafer; and an operating device for operating the wafer position movement; wherein the operating device is arranged between the placing device and the oxidizing device and is arranged at the same side of the detecting device. The utility model discloses can carry out the carrier life-span to the silicon chip of same model in batches and detect, the test result is accurate, and every group test time is short, and automated control is accurate, whole linkage nature is good, and structural design is compact and reasonable, and occupation space is little, and efficiency of software testing is high.
Description
Technical Field
The utility model belongs to the technical field of semiconductor wafer test, especially, relate to a wafer life-span test equipment.
Background
The non-equilibrium minority carrier lifetime (minority carrier lifetime) is an important parameter of a silicon crystal material, is directly related to impurities and a crystal structure in a single crystal wafer, and has an important influence on the performance of a semiconductor device, so that the accurate detection of the minority carrier lifetime of the silicon single crystal wafer is particularly important in the production process of the semiconductor material. There are many methods for measuring the lifetime of the unbalanced minority carrier, which belong to two major categories, namely a transient method and a steady-state method. The transient state method is to excite non-equilibrium carrier in semiconductor by pulse electricity or flash light, change the bulk resistance of semiconductor and obtain the life of semiconductor material directly by measuring the change rule of bulk resistance or terminal voltage. The steady state method is a method of measuring some physical quantities of a semiconductor sample in a stable non-equilibrium state to obtain the lifetime of a carrier by using stable illumination, namely, the distribution of non-equilibrium minority carriers in the semiconductor reaches a stable state, such as a surface photovoltage method, a steady state photoconductive method and the like.
The life test method usually adopts a high-frequency photoconductive decay method (H-PCD), which is mainly used for detecting the surface life and the bulk life of the wafer, but the detected surface life data is not accurate and the overall life of the wafer cannot be completely expressed; the overall life of the wafer can be better reflected. Since the lifetime of the contamination-related body needs to be determined when the lifetime of the wafer is measured, the recombination process on the surface of the wafer needs to be inhibited, i.e. the surface of the wafer sample needs to be passivated. The passivation mode that usually adopts is chemical passivation, and chemical passivation operating process is loaded down with trivial details, complicated, wastes time and energy, uses chemical passivation method simultaneously and needs to use chemical reagent, has great harm to the environment, does not accord with the environmental protection requirement, and increases enterprise manufacturing cost.
SUMMERY OF THE UTILITY MODEL
In order to solve the technical problem, the utility model discloses a technical scheme is:
a wafer life test apparatus comprising:
a placing device for placing the wafer;
the oxidation device is used for oxidizing the surfaces of the two sides of the wafer;
the detection device is used for sequentially passivating the surfaces of two sides of the oxidized wafer and testing the service life of a current carrier on the surface of one passivated wafer;
and an operating device for operating the wafer position movement;
wherein, the placing device, the oxidation device and the detection device are arranged around the operation device.
Furthermore, the placing device comprises a wafer basket for bearing the wafer, the placing direction of the wafer basket is consistent with the moving-out direction of the wafer, and the opening direction of the wafer basket is arranged towards one side of the operating device.
Further, the oxidation device comprises a sealing cavity, and the sealing cavity is internally provided with:
the clamping component is used for fixing the wafer and suspending the wafer;
a heater for heating the surface of the wafer;
and a vent assembly for venting the sealed cavity;
the clamping component is arranged at the bottom of the sealed cavity and is positioned right below the heater, so that the wafer can be horizontally placed and the surfaces of the two sides of the wafer are exposed;
the ventilation assembly is arranged on the side face of the sealing cavity and close to the clamping assembly.
Furthermore, the clamping and fixing component comprises a plurality of L-shaped clamping heads which are uniformly distributed and thin columns which are used for supporting the clamping heads and are respectively and independently connected with the clamping heads, and a circle which is formed by the surrounding of the clamping heads is matched with the excircle of the wafer.
Further, the ventilation assembly comprises an oxygen pipe for introducing oxygen into the sealed cavity so as to enable the double-side surfaces of the wafer to be oxidized and a nitrogen pipe for introducing nitrogen so as to reduce the temperature of the surface of the wafer.
Further, detection device includes the detection room, be equipped with in the detection room:
a placing table for placing the wafer and horizontally placing the wafer;
the electron injector is used for respectively scattering charges to the surfaces of the two sides of the wafer;
the test probe is used for testing the service life of the carriers on the upper surface of the wafer;
the electron injectors are symmetrically arranged relative to the wafer;
the detection probe is arranged at the top of the detection chamber and is arranged behind the electronic injector.
Furthermore, the wafer is suspended on the placing table, and the surfaces of both sides of the wafer are exposed.
Further, the placing table comprises a clamping table used for placing the wafer and arranged in contact with the outer edge of the wafer, and a support column connected with the clamping table and used for supporting the clamping table; the number of the supporting columns is matched with the number of the clamping tables.
Further, the electronic injector and the test probe are arranged side by side and are both perpendicular to the surface of the wafer.
Further, the operating device comprises a manipulator which can clamp the wafer and operate the wafer to freely rotate and move.
Compared with the prior art, the utility model provides a test system can carry out the carrier life-span to the wafer of same model in batches and detect, and the test result is accurate, and every group test time is short, and this system need not to use chemical reagent to passivate simultaneously, and test system automated control is accurate, whole linkage nature is good, and structural design is compact and reasonable, and occupation space is little, and efficiency of software testing is high.
Drawings
Fig. 1 is a top view of a testing apparatus according to a first embodiment of the present invention;
fig. 2 is a schematic structural diagram of a placement device according to an embodiment of the present invention;
FIG. 3 is a schematic structural view of an oxidation apparatus according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a detection device according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a moving path of a test probe according to an embodiment of the present invention;
fig. 6 is an enlarged schematic view of a portion a according to an embodiment of the present invention;
fig. 7 is a top view of a testing apparatus according to a second embodiment of the present invention;
fig. 8 is a top view of a testing apparatus according to a third embodiment of the present invention;
fig. 9 is a process flow diagram of an embodiment of the present invention;
FIG. 10 is a graph showing a change in lifetime of the entire single crystal silicon rod according to an embodiment of the present invention.
In the figure:
10. placing device 11, sheet basket 12 and platform surface
13. Elevating platform 14, air cylinder 20 and operating device
21. Manipulator 30, oxidation device 31 and sealed cavity
32. Clamping component 321, clamping head 322 and thin column
33. Heater 34, oxygen pipe 35, nitrogen gas pipe
40. Detection device 41, detection chamber 42, and placement table
421. Clamping table 422, support column 43 and electronic injector
44. Test probe 45, line 50, wafer
51. Oxide film 52, V-groove 53, diameter
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The embodiment provides a life test device for a polished wafer, which is mainly used for life test of the polished wafer, and as shown in fig. 1, the life test device comprises a placing device 10 for placing a wafer 50, an oxidizing device 30 for oxidizing the surfaces on both sides of the wafer 50, a detecting device 40 for sequentially passivating the surfaces on both sides of the oxidized wafer 50 and testing the life of carriers on the surface of one passivated wafer 50, and an operating device 20 for operating the position movement of the wafer 50. Wherein, the placing device 10, the oxidation device 30 and the detection device 40 are disposed around the operation device 20. In the present embodiment, the operating device 20 is disposed between the placing device 10 and the oxidizing device 30, and is disposed on the same side as the detecting device 40; the operating device 20 takes the wafer 50 out of the placing device 10 and places the wafer 50 in the oxidizing device 30 for oxidation, so that an oxide film 51 is formed on both surfaces of the wafer 50; the operation device 20 takes the oxidized wafer 50 out of the oxidation device 30, horizontally arranges the oxidized wafer 50, places the oxidized wafer in the detection device 40, passivates the surfaces of the oxidized wafer 50 by charge deposition, and detects the service life of the surface of one passivated wafer 50, thereby measuring the carrier life of the surface of the wafer 50. The tested wafer 50 is removed from the inspection device 40 by the handling device 20 and placed back in the original position of the placement device 10. The placing device 10 is simultaneously moved upwards to place the next wafer 50 to be tested at the position grasped by the handling device 20, and the above operation is continued for subsequent automatic inspection. Specifically, as shown in fig. 2, the placing device 10 includes a wafer basket 11 for carrying wafers 50, the structure of the wafer basket 11 is adapted to the wafers 50, and the structure of the wafer basket 11 is only required to be capable of placing a plurality of groups of wafers 50; the wafer basket 11 is placed in the same direction as the wafer 50 is removed, and preferably, the wafer basket 11 is placed horizontally on the table surface 12 with its opening oriented toward the side of the handling device 20, ensuring that one surface of the wafer 50 is oriented horizontally upward. The wafer 50 to be tested can be any single wafer, or a plurality of groups of wafers on different parts of any whole single crystal silicon rod, or a group of wafers, but the wafer 50 to be tested in each batch must be of a uniform specification and size, and the device for bearing the wafer 50 in multiple batches can effectively prevent the probability of misplacing or misplacing the wafer 50, accurately take and place the wafer, is beneficial to saving the operation time and improving the equipment utilization rate.
The wafer basket 11 is clamped and fixedly placed on the platform surface 12, the platform surface 12 is provided with a lifting platform 13 which can be integrally fixed with the wafer basket 11 and can vertically move up and down, a cylinder 14 arranged below the lifting platform 13 can drive the lifting platform 13 and the wafer basket 11 to vertically move up and down, and mainly when a plurality of wafers 50 are matched for continuous life test, the operated wafer 50 needs to be matched with the operation height position of a manipulator 21 in the operation device 20, namely after the last group of wafers 50 are operated, the cylinder 14 is operated again to push the lifting platform 13 to drive the wafer basket 11 to vertically move up, so that the position of the next group of wafers 50 just corresponds to the operation height of the manipulator 21.
Further, the handling apparatus 20 includes a single robot 21, the robot 21 includes a retractable arm and a gripper, the gripper is adapted to the outer edge of the wafer 50, the robot 21 is a conventional structure in the art, and the drawings are omitted, and the robot 21 can automatically clamp the wafer 50 and operate the wafer 50 to freely rotate horizontally.
The oxidation device 30 is located on the same horizontal axis as the placement device 10 and the operation device 20, and is disposed on the side of the operation device 20 away from the placement device 10. As shown in fig. 3, the oxidation apparatus 30 includes a sealed chamber 31, and an open end of the sealed chamber 31 is disposed toward one side of the operation apparatus 20. A clamping component 32 for fixing the wafer 50 and suspending the wafer 50, a heater 33 for heating the surface of the wafer 50 and a ventilation component for ventilating the inside of the sealed cavity 31 are arranged in the sealed cavity 31. The clamping component 32 comprises a plurality of L-shaped clamping heads 321 which are uniformly distributed and thin columns 322 which are used for supporting the clamping heads 321 and are respectively and independently connected with the clamping heads 321, all the thin columns 322 are arranged at the same height, and a circle defined by the clamping heads 321 is matched with the outer circle of the wafer 50, so that the two sides of the wafer 50 can be exposed and arranged, and the wafer 50 can be suspended, and the oxidation of the surfaces of the two sides of the wafer 50 is facilitated. The clamping and fixing component 32 is integrally located at the middle position of the bottom of the sealed cavity 31 and right below the heater 33, in order to ensure that the wafer 50 is uniformly heated and oxidized in the sealed cavity 31, the clamping and fixing component 32 is set to be a fixed structure, and the ventilation component is arranged on the side surface of the sealed cavity 31 and above one side close to the clamping and fixing component 32. The ventilation assembly mainly comprises an oxygen pipe 34 for introducing oxygen into the sealed cavity 31 to oxidize the surfaces of the two sides of the wafer 50 and a nitrogen pipe 35 for introducing nitrogen to reduce the temperature of the surface of the wafer 50, wherein the oxygen pipe 34 and the nitrogen pipe 35 are arranged on the same side. Preferably, the heater 33 is a plurality of ultraviolet lamps disposed side by side, and the ultraviolet lamps may be disposed side by side or at intervals right above the wafer 50 and at the center of the wafer 50, which is not limited herein.
In the present embodiment, the whole testing process is performed in a closed environment, so that the surface of the wafer 50 is horizontally disposed in the sealed chamber 31 after the wafer 50 is stably placed on the clamping component 32. Closing the sealed cavity 31, namely, controlling the heater 33 of the ultraviolet lamp to heat the surface of the wafer 50, wherein the wafer 50 is always stable and immobile in the sealed cavity 31 in the whole process; when the heating temperature reaches 400-500 ℃, the heater 33 is stopped to heat and the temperature is kept unchanged, and the exposed wafer 50 is influenced by the temperature radiated by the heater 33 in the sealed cavity 31, so that the upper surface and the lower surface of the wafer 50 which are horizontally arranged are heated; meanwhile, the oxygen pipe 34 is synchronously controlled to introduce oxygen into the sealed cavity 31, the oxygen lasts for 3-8min at the temperature of 400-. After the oxide film 51 is formed, in order to reduce the temperature in the sealed cavity 31, nitrogen needs to be introduced into the sealed cavity 31 through the nitrogen pipe 35, the nitrogen introduction time is 2-5min, so as to reduce the temperature of the surface of the wafer 50, and the temperature of the surface of the wafer 50 finally obtained after the nitrogen introduction is room temperature, so that charge deposition and microscopic carrier life test can be conveniently performed on the surface of the wafer 50 subsequently. In the present embodiment, the flow rates of oxygen and nitrogen are related to the cross sections of the oxygen pipe 34 and the nitrogen pipe 35, respectively, and are not specifically required here. Meanwhile, in order to facilitate monitoring of the temperature in the sealed chamber 31, a temperature sensor for monitoring the heating temperature of the heater 33 and the surface of the wafer 50 after the nitrogen gas is introduced is provided in the sealed chamber 31, and the drawings are omitted.
The detection device 40 and the operation device 20 are longitudinally arranged in parallel and are positioned between the placing device 10 and the oxidation device 30, the arrangement enables the oxidized wafer 50 to be placed in the adjacent detection device 40 for detection after being directly rotated by 90 degrees, the detected wafer 50 returns to the wafer basket 11 in the placing device 10 after being rotated by 90 degrees, all operation routes are shortest and used for the least, the operation routes are intersected with other positions for swinging, the operation process of the structure is the simplest, the efficiency is high, and the equipment utilization rate is the highest.
As shown in fig. 4, the inspection apparatus 40 includes an inspection chamber 41, and a placing stage 42 configured to horizontally place the wafer 50 and to expose and suspend both side surfaces of the wafer 50, a passivation unit configured to passivate both side surfaces of the oxidized wafer 50, and an inspection unit configured to perform a carrier lifetime test on a surface of one of the passivated wafers 50 are provided in the inspection chamber 41. Wherein, the passivation parts are arranged at both sides of the placing table 42, and the detection part is adjacent to one passivation part at the same side; the passivation unit and the inspection unit move in the same radial direction of the wafer 50; the passivation is disposed in front of the detection portion in a direction in which the passivation moves.
Specifically, the passivation portion includes electron injectors 43 symmetrically disposed on two sides of the wafer 50, respectively fixed at the top and the bottom of the detection chamber 41, and configured to scatter charges to oxidized surfaces of the wafer 50 on both sides; the inspection section includes a test probe 44 disposed at the top of the inspection chamber 41 and used for testing the lifetime of carriers on the upper surface of the wafer 50, the test probe 44 being disposed behind the electron flood apparatus 43. In this embodiment, charges are first scattered on the surfaces of the oxidized wafer 50 on both sides, so that the surface of the wafer 50 is sufficiently passivated, and the test probe 44 is used to perform the lifetime test of the carriers.
Specifically, the placing table 42 includes a plurality of clamping tables 421 which are uniformly arranged and used for placing the wafer 50 and are arranged in contact with the outer edge of the wafer 50, and supporting columns 422 which are connected with the clamping tables 421 and used for supporting the clamping tables and are independently arranged, and the number of the clamping tables 421 is matched with that of the supporting columns 422. The structure of the clamping table 421 and the support 422 can be the same as that of the clamping head 321 and the thin column 322, i.e. both are L-shaped structures; other configurations of the apparatus are also possible, not specifically described herein, in order to suspend the wafer 50 horizontally and expose both surfaces of the wafer 50, so that the electron injector 43 can easily spray charges onto both surfaces of the wafer 50. The electron beam injector 43 and the test probe 44 are disposed perpendicular to the surface of the wafer 50, the electron beam injector 43 is symmetrically disposed on both sides of the wafer 50 and opposite to the surface of the wafer 50, and the electron beam injector 43 is a device commonly used in the art for injecting charges and is omitted here. The testing probe 44 is arranged on one side surface of the wafer 50, in the embodiment, the testing probe 44 is arranged on the top of the detection chamber 41, is arranged in a slide way on the top along the same radial direction with the electron injector 43, and the testing probe 44 is arranged behind the electron injector 43, during the passivation process, the electron injector 43 moves horizontally along the slide way, and after each group of data is tested, the electron injector 43 pushes forwards along the direction vertical to the horizontal movement of the electron injector to push downwardsScattering charges on the surface positions of a group of wafers 50; correspondingly, in the detection process, the test probe 44 moves in the same direction and the same diameter to detect along with the electronic injector 43; as to how to control the positions of the electronic injector 43 and the test probe 44, a slide control structure, a pneumatic control structure, or a hydraulic control structure commonly used in the art may be employed, and is not particularly limited herein. The charge deposited on the SiO by the electron injector 43 projected onto the surface of the wafer 502An electric field is generated at the Si interface, attracting carriers of opposite electrical polarity and repelling carriers of the same electrical polarity, such that the electric field separates electrons and holes, reducing the likelihood of surface recombination, thereby increasing the test signal of test probe 44.
In the inspection apparatus 40, passivation and lifetime tests are performed on the surface of the wafer 50 continuously along the set path 45 in the same direction in the set area, that is, the path 45 is parallel to the slide and is disposed up and down correspondingly, the position of the path 45 put on the wafer 50 is specifically as shown in fig. 5, and the position to be tested can be set by the controller in advance to set the area to be tested, which is a common operation mode in the field and is omitted here. The path taken by the charges irradiated by the electron injector 43 onto the oxide film 51 in the set region on the two side surfaces of the wafer 50 is the same as the path taken by the testing probe 44 for detecting the minority carrier lifetime of the wafer 50 after the charges are passivated, that is, the path 45 is obtained.
Further, the route 45 is a continuous straight line, the route 45 is perpendicular to the diameter 53 corresponding to the V-groove 52 in the wafer 50, the V-groove 52 is configured as shown in fig. 6, and the distance between adjacent routes is 0.5-8 mm.
During testing, the test probe 44 is moved along the path 45 from the left side of the wafer 50 to the right side thereof at the set speed V1 in the same direction, and simultaneously the test probe 44 is moved in turn from the end far from the V-groove 52 to the end close to the V-groove 52 at the set speed V2 in synchronization with the electron injector 43, as shown by the arrows in fig. 5, as for the settings of V1 and V2, the settings may be determined according to the actual circumstances, and are not specifically required. That is, the electron injector 43 firstly scatters charges on the surfaces of both sides of the wafer 50 along the route 45 in front, so as to fully passivate the surface of the wafer 50, and reduce the possibility of surface charge recombination, so that the bulk life of the wafer 50 to be tested is more accurate, the test probe 44 then performs microwave detection on the surface of the wafer 50 generating free electron holes, the test probe 44 is an electronic tester commonly used in the field, and the working principle and the drawings thereof are omitted here; the data measured by the test probe 44, which is the lifetime distribution of minority carriers on the surface of the wafer 50, is then collected and collated.
The electronic injector 43 and the test probe 44 are both arranged at a position far away from one side of the V-shaped groove 52 of the wafer 50 and are both arranged at one side of any side of the wafer 50, in the present embodiment, at the left side of the wafer 50, in the detection process, the test probe 44 and the electronic injector 43 move from the left side of the wafer 50 to the right along the route 45 to the outer edge of the wafer 50, the test machine can measure a group of data, that is, the data is the carrier lifetime value corresponding to the vertical intersection point of the route 45 and the diameter 53 in the horizontal radial direction of the wafer 50, and simultaneously, after the group of route 45 data is tested, the electronic injector 43 and the test probe 44 synchronously move from one end far away from the V-shaped groove 52 to the direction close to one end of the V-shaped groove 52 in sequence, so as to automatically obtain a plurality of groups of average lifetime data values, that is to obtain the lifetime distribution of the wafer 50 in, which is the lifetime value of the wafer 50.
Of course, the positions of the oxidation device 30 and the detection device 40 in the second embodiment can be interchanged compared to the first embodiment, and the structure is as shown in fig. 7, that is, the placing device 10, the operation device 20 and the detection device 40 are sequentially arranged on the same horizontal line, and the oxidation device 30 is separately located at one side of the operation device 20. Or the position of the placing device 10 and the position of the detecting device 40 are exchanged in the third embodiment, the structure is as shown in fig. 8, that is, the oxidizing device 30, the operating device 20 and the detecting device 40 are sequentially arranged on the same horizontal line, and the placing device 10 is separately arranged at one side of the operating device 20. In any case, the opening of the wafer basket 11 in the placing device 10, the opening of the sealing chamber 31 in the oxidation device 30, and the opening of the detection chamber 41 in the detection device 40 are disposed toward the operation device 20, and the operation steps of removing, oxidizing, passivating, detecting, and replacing can be sequentially performed.
The utility model provides a life-span test equipment can carry out the carrier life-span to the wafer 50 of the same model after the polishing in batches and detect, and the test result is accurate, and every group test time is short, and this equipment need not to use chemical reagent to passivate simultaneously, and test equipment automated control is accurate, whole linkage nature is good, and structural design is compact and reasonable, and occupation space is little, and efficiency of software testing is high.
The present embodiment provides a method for testing lifetime of a wafer, as shown in fig. 9, the method includes the steps of:
a method for testing the service life of a wafer comprises the following steps:
s1: oxidation, i.e., formation of an oxide film 51 on both surfaces of the wafer 50.
The wafer 50 placed on the placing device 10 is horizontally placed in the sealed cavity 31 in the oxidation device 30 through the manipulator 21, namely, the manipulator 21 clamps and fixedly grabs a group of wafers 50, and then the wafers are horizontally placed on the clamping component 32 in the sealed cavity 31, so that the wafers 50 are horizontally suspended, the surfaces of two sides of the wafers are exposed, and the manipulator 21 is retracted.
The sealed chamber 31 is closed, i.e. the heater 33 of the ultraviolet lamp is controlled to heat the surface of the wafer 50, and the wafer 50 is kept still on the clamping assembly 32 in the sealed chamber 31 in the whole process. When the heating temperature reaches 400-500 ℃, the heater 33 is stopped to heat and the temperature is kept unchanged, and the exposed wafer 50 is influenced by the temperature radiated by the heater 33 in the sealed cavity 31, so that the upper surface and the lower surface of the wafer 50 which are horizontally arranged are heated; meanwhile, the oxygen tube 34 is synchronously controlled to introduce oxygen into the sealed cavity 31, the oxygen lasts for 3-8min at the temperature of 400-500 ℃, the oxygen is easy to form ozone at the temperature of 400-500 ℃, and correspondingly, the ozone reacts with silicon on the two side surfaces of the wafer 50, so that the two sides of the wafer 50 are oxidized to respectively form a layer of silicon dioxide oxide film 51 with the thickness of 3-5 nm. The silicon dioxide oxide film 51 is more beneficial to subsequent charge deposition passivation, chemical passivation which causes great environmental pollution in the prior art is not needed, the passivation time is saved, the passivation effect is good, and the uniformity is good. After the oxide film 51 is formed, in order to reduce the temperature in the sealed chamber 31, nitrogen gas needs to be introduced into the sealed chamber 31 through the nitrogen gas pipe 35, and the nitrogen gas introduction time is 2-5min, so as to reduce the temperature of the surface of the wafer 50, in this embodiment, the temperature of the surface of the wafer 50 finally obtained after the nitrogen gas introduction is room temperature.
S2: passivation, i.e., the deposition of electric charges on both side surfaces of the wafer 50 having the oxide film 51.
The manipulator 21 takes the oxidized wafer 50 out of the closed cavity 31 and transfers the oxidized wafer to the placing table 42 in the detection device 40, and the surfaces of both sides of the wafer 50 are exposed and suspended; the electron sprayers 43 which are symmetrically arranged at the top and the bottom of the detection chamber 41 and are symmetrically arranged at the two sides of the wafer 50 are controlled to spray charges on the set areas of the two side surfaces of the wafer 50 along the set route 45 in the same direction and continuously, so that the surface of the wafer 50 is fully passivated, and a test probe 44 which is arranged on the single side surface of the wafer 50 is used for carrying out a carrier life test.
During passivation, the electron flood apparatus 43 moves horizontally along the slide, and after each set of data is tested, the electron flood apparatus 43 advances in a direction perpendicular to its horizontal movement to charge the surface locations of the next set of wafers 50. The charge deposited on the SiO by the electron injector 43 projected onto the surface of the wafer 502An electric field is generated at the Si interface, attracting carriers of opposite electrical polarity and repelling carriers of the same electrical polarity, such that the electric field separates electrons and holes, reducing the likelihood of surface recombination, thereby increasing the test signal of test probe 44.
S3: and testing, namely performing a life test on one surface of the passivated wafer 50.
During testing, the test probe 44 is moved along the path 45 from the left side of the wafer 50 to the right side thereof at the set speed V1 in the same direction, and simultaneously the test probe 44 is moved in sequence from the end far from the V-groove 52 to the end near the V-groove 52 at the set speed V2 in synchronization with the electron injector 43, as indicated by the arrow in fig. 5. I.e. the test probe 44 only performs carrier lifetime measurements on the upwardly disposed surface of the wafer 50, which moves with the electron injector 43 from the left side of the wafer 50 to the right along line 45 to the outer edge of the wafer 50, the tester can measure a set of data, this data is the carrier lifetime value corresponding to the vertical intersection of line 45 and diameter 53 at the horizontal radial direction of wafer 50, meanwhile, after the test probe 44 finishes testing the data of a group of routes 45, the test probe synchronously moves from one end far away from the V-shaped groove 52 to one end close to the V-shaped groove 52 along with the electronic ejector 43 in sequence, a plurality of groups of service life data values are automatically obtained, the minority carrier lifetime distribution on the surface of the wafer 50 can be obtained, statistical analysis is performed on the obtained data, and relevant data representing the lifetime of the surface of the wafer 50, such as the average value, the median, the maximum value, the minimum value, the standard deviation and the like, are calculated.
The electron injector 43 is used to apply charges to the surfaces of both sides of the wafer 50 covered with the oxide film 51, and the deposited charges passivate the surfaces of both sides of the wafer 50, reducing the possibility of surface charge recombination, resulting in more accurate life span of the wafer 50 under test. The method also saves the flow of carrying out oxidation passivation on the surface of the wafer 50 by using chemical liquid medicine before testing in the prior art, and also avoids the corrosion to a testing machine and the pollution to the working environment due to the chemical passivation; and the charge deposition does not negatively affect the measured minority carrier lifetime.
The charge deposited on the SiO by the electron injector 43 projected onto the surface of the wafer 502An electric field is generated at the Si interface, attracting carriers of opposite electrical polarity and repelling carriers of the same electrical polarity, such that the electric field separates electrons and holes, reducing the likelihood of surface recombination, thereby increasing the test signal of test probe 44.
For the life test of the whole single crystal silicon rod or the whole section of the single crystal silicon rod, the average life value of all the routes 45 in each wafer 50 of each section is determined as the life value of the wafer 50, and then possible problems in the crystal pulling process are fed back according to the life values of the wafers 50, and responses are made in time.
After a wafer 50 is tested, the wafer 50 is placed back into the wafer basket 11 of the placement device 10 by the robot 21.
The re-operation cylinder 14 pushes the lifting platform 13 to drive the wafer basket 11 to move vertically upwards, so that the position of the next group of wafers 50 just corresponds to the operation height of the robot 21. The above steps are repeated again, and the next set of wafers 50 is tested in sequence.
The utility model discloses a theory of operation: respectively oxidizing the surfaces of the two sides of the wafer 50 at the temperature of 400-500 ℃ to form a layer of oxide film 51, laser-exciting and scattering charges on the surfaces of the two sides of the wafer 50 with the oxide film 51 through an electronic injector 43 to deposit and passivate the charges on the surfaces of the two sides of the wafer 50, and irradiating microwave signals emitted by a test probe 44 onto the upward horizontal surface of the wafer 50 to detect carriers. The pulsing of the infrared semiconductor laser causes the area under test on the wafer 50 to generate free electron-hole pairs whose concentration and conductivity decrease upon excitation due to recombination of free electrons and holes. The attenuated conductivity can be monitored by detecting the microwave reflectivity, since the reflected microwave power is dependent on the conductivity of the wafer 50. The possibility of surface electron-hole pair recombination is reduced by the process of scattering charges on the wafer 50, so that the surface is fully passivated, the influence of the surface life on the test is eliminated, and the life of the tested wafer is the bulk life. Thus, the probability of surface recombination is low and surface passivation is very effective.
The first embodiment is as follows:
dividing a single crystal silicon rod with the diameter of 300mm into three sections from head to tail, namely a head 1#, a middle 2# and a tail 3# respectively, taking a plurality of wafers 50 from the head 1#, the middle 2# and the tail 3# according to the positions of the sections from head to tail, and marking the positions of the wafers 50 at the sections, such as: the 1-002 tablet is the 2 nd tablet in the 1# of the head part, and the 2-102 tablet is the 102 nd tablet in the 2# of the middle part. In this example, the 2 nd and 102 th slices of the head # 1, i.e., 1-002, 1-102, respectively, are selected; the 2 nd, 102 th and 202 nd tablets of the middle part 2#, i.e. 2-002, 2-102 and 2-202, respectively; the 2 nd, 102 th and 202 nd slices of the tail 3#, i.e., 3-002, 3-102 and 3-202, respectively. The life data obtained by the above steps are shown in table 1; meanwhile, according to the data in table 1, the graph obtained by taking the position of the wafer 50 in the single crystal silicon rod and taking the head part 1# to the tail part 3# as the horizontal radial X axis and the service life as the Y axis is shown in fig. 10, wherein a is the maximum service life value, b is the average service life value, and c is the minimum service life value, and it can be seen from fig. 10 that the service life data of the head part 1# of the single crystal silicon rod is obviously higher than the service life data of the tail part 3# of the single crystal silicon rod.
TABLE 1 Life data for each site wafer in a 300 diameter single crystal silicon rod
Compared with the prior art, the utility model discloses test method need not to carry out chemical passivation to the wafer for nondestructive test, can detect the internal carrier life-span of wafer in batches, and the test result is accurate and efficiency of software testing is high, can continue to carry out the detection and the test in the aspect of other physicochemical property to the wafer after the test is accomplished, improves the utilization ratio of wafer, practices thrift the cost.
The embodiments of the present invention have been described in detail, and the description is only for the preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. All the equivalent changes and improvements made according to the application scope of the present invention should still fall within the patent coverage of the present invention.
Claims (10)
1. A wafer life test apparatus, comprising:
a placing device for placing the wafer;
the oxidation device is used for oxidizing the surfaces of the two sides of the wafer;
the detection device is used for sequentially passivating the surfaces of two sides of the oxidized wafer and testing the service life of a current carrier on the surface of one passivated wafer;
and an operating device for operating the wafer position movement;
wherein, the placing device, the oxidation device and the detection device are arranged around the operation device.
2. The wafer life test apparatus as set forth in claim 1, wherein the placing device comprises a wafer basket for carrying the wafer, the placing direction of the wafer basket is consistent with the direction in which the wafer is removed, and the opening direction of the wafer basket is set toward the operating device side.
3. The wafer life test apparatus as set forth in claim 1 or 2, wherein the oxidation means includes a sealed chamber in which:
the clamping component is used for fixing the wafer and suspending the wafer;
a heater for heating the surface of the wafer;
and a vent assembly for venting the sealed cavity;
the clamping component is arranged at the bottom of the sealed cavity and is positioned right below the heater, so that the wafer can be horizontally placed and the surfaces of the two sides of the wafer are exposed;
the ventilation assembly is arranged on the side face of the sealing cavity and close to the clamping assembly.
4. The wafer life test device as claimed in claim 3, wherein the clamping component comprises a plurality of L-shaped clamping heads distributed uniformly and thin columns used for supporting the clamping heads and respectively and independently connected with the clamping heads, and a circle enclosed by the clamping heads is matched with the outer circle of the wafer.
5. The wafer life test equipment as recited in claim 4, wherein the ventilation assembly comprises an oxygen pipe for introducing oxygen into the sealed chamber to oxidize the double-side surface of the wafer and a nitrogen pipe for introducing nitrogen to reduce the temperature of the surface of the wafer.
6. The wafer life test apparatus as set forth in any one of claims 1 to 2 and 4 to 5, wherein the detection device comprises a detection chamber, and the detection chamber is provided with:
a placing table for placing the wafer and horizontally placing the wafer;
the electron injector is used for respectively scattering charges to the surfaces of the two sides of the wafer;
the test probe is used for testing the service life of the carriers on the upper surface of the wafer;
the electron injectors are symmetrically arranged relative to the wafer;
the detection probe is arranged at the top of the detection chamber and is arranged behind the electronic injector.
7. The wafer life test apparatus as claimed in claim 6, wherein the wafer is suspended on the placing stage and both surfaces of the wafer are exposed.
8. The wafer life test apparatus as set forth in claim 7, wherein the placing table includes a chuck table for placing the wafer and disposed in contact with an outer edge of the wafer, and a support column connected to the chuck table and supporting the chuck table; the number of the supporting columns is matched with the number of the clamping tables.
9. The wafer life test apparatus as recited in claim 6, wherein the electron injector and the test probe are arranged side by side and are perpendicular to the wafer surface.
10. The wafer life test apparatus as set forth in any one of claims 1 to 2, 4 to 5 and 7 to 9, wherein the handling device comprises a robot which can hold the wafer and handle the wafer to move freely in rotation.
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| CN202022530874.1U CN213212113U (en) | 2020-11-05 | 2020-11-05 | Wafer life test equipment |
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