CN115938927A - Ultrathin wafer thinning process - Google Patents
Ultrathin wafer thinning process Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 78
- 238000000227 grinding Methods 0.000 claims abstract description 143
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- 238000000137 annealing Methods 0.000 claims abstract description 15
- 238000001039 wet etching Methods 0.000 claims abstract description 11
- 230000005855 radiation Effects 0.000 claims abstract description 9
- 238000001723 curing Methods 0.000 claims abstract description 7
- 238000005530 etching Methods 0.000 claims description 50
- 239000000853 adhesive Substances 0.000 claims description 34
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- 239000011347 resin Substances 0.000 claims description 25
- 229920005989 resin Polymers 0.000 claims description 25
- 239000011521 glass Substances 0.000 claims description 22
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 20
- 239000007788 liquid Substances 0.000 claims description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
- 239000011248 coating agent Substances 0.000 claims description 14
- 238000000576 coating method Methods 0.000 claims description 14
- 238000003848 UV Light-Curing Methods 0.000 claims description 13
- 239000000110 cooling liquid Substances 0.000 claims description 12
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 10
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- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
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- 238000004519 manufacturing process Methods 0.000 abstract description 8
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- 238000005452 bending Methods 0.000 description 3
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 3
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- 241000251468 Actinopterygii Species 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention relates to the technical field of ultrathin wafer preparation, in particular to an ultrathin wafer thinning process.A wafer surface and a fixed carrier are fixedly bonded through photoresist, the thickness of bonding and curing is controlled to be uniform, wet etching is continuously carried out on a grinding surface after a wafer back grinding process, a wafer back grinding damage layer is eliminated, and then the fixed carrier is stripped and the photoresist is removed; the wafer can be thinned through the fixed carrier to play a role of a rigid structure for supporting, and the surface of the wafer is protected from being influenced in the process by matching with the photoresist; the photoresist can realize rapid curing bonding or later stripping, which is beneficial to improving the production efficiency; the laser radiation annealing process and the wet etching process are arranged in the back grinding process to treat the surface of the wafer, so that the warping degree can be reduced, the flatness of the surface of the wafer can be better, the warping degree can be further reduced under the back grinding condition, the lower warping degree and the better flatness can be realized in the process of preparing the ultrathin wafer, and the yield can be improved.
Description
Technical Field
The invention relates to the technical field of ultrathin wafer preparation, in particular to an ultrathin wafer thinning process.
Background
The wafer refers to a silicon wafer used for manufacturing a silicon semiconductor integrated circuit, and is called a wafer because the shape is circular; various circuit device structures can be fabricated on a silicon wafer to form an IC product with specific electrical functions. With the development of semiconductor manufacturing industry, the trend and the requirement for thinning the wafer thickness are more and more obvious, so as to manufacture ultra-thin chips.
At present, the commonly used thinning technology in the semiconductor industry is grinding type thinning, which is widely used for removing silicon materials of semiconductor wafers, and the surfaces of the wafers are uniform after grinding type thinning; the wafer is polished by the grinding wheel, but the wafer needs to be fixed in the polishing process, so that the wafer is inconvenient to separate and easy to damage in the later period; and grinding wheel direct friction sample surface is mainly adopted in grinding process to thin, the grinding force of grinding can be influenced by the abrasive grain diameter on the grinding wheel, then the speed is influenced, if the grain diameter is larger, higher grinding force can be realized, the thinning speed is high, but the processing quality is low, and a large number of scratches are easy to appear on the thinning surface.
In addition, the wafer thinning process is easy to cause serious local deformation of the wafer due to large internal stress and loss of thickness rigid support in the grinding process, especially for the preparation of ultrathin wafers, and the bending or warping phenomenon is easy to occur after the thickness of the wafer is thinned, so that the stability and the service performance of products after the process production are directly influenced. Therefore, there is a need for an ultra-thin wafer thinning process, which can avoid or reduce the bending or warping of the ultra-thin wafer during the process, and reduce the surface damage, i.e., better surface planarization. In view of this, we propose an ultra-thin wafer thinning process.
Disclosure of Invention
In order to make up for the defects, the invention provides an ultrathin wafer thinning process.
The technical scheme of the invention is as follows:
an ultrathin wafer thinning process specifically comprises the following steps: fixing and bonding the surface of the wafer and the fixed carrier through photoresist, controlling the thickness of bonding and curing to be uniform, fixing the fixed carrier on the grinding pad, continuously carrying out wet etching on the grinding surface after the wafer back grinding process, stripping the fixed carrier and removing the photoresist after a wafer back grinding damaged layer is eliminated, attaching a dicing film or a scribing film, and finishing dicing according to the requirement.
Specifically, the rigidity effect that the fixed carrier that is equipped with can play the support avoids at the attenuate in-process, and wafer thickness reduces gradually and loses the support of thickness rigidity intensity and the local deformation condition that appears, and the surface unevenness appears promptly, the warpage phenomenon appears, hinders and influences the yield then to cooperate the photoresist adhesion to can avoid other process such as later stage backgrinding to damage the wafer surface, the photoresist also can be regarded as one deck protective layer promptly, avoids the fish tail wafer.
Preferably, the fixed carrier is a transparent carrier plate or carrier glass with a flat and light-transmitting surface, and the photoresist is any one or more of UV-curing flexible resin adhesive or UV-decomposing flexible resin adhesive. The UV decomposition type flexible resin adhesive can lose viscosity through ultraviolet irradiation, so that the adhesive can be peeled off.
Preferably, the specific process steps of the photoresist fixing and bonding are as follows: respectively and uniformly coating UV curing type flexible resin adhesive or UV decomposition type flexible resin adhesive on the surface of the wafer or the surface of the fixed carrier corresponding to the surface of the wafer through a spin coater, correspondingly attaching the fixed carrier and the surface of the wafer coated with the photoresist, and controlling environmental conditions in advance to enable the UV curing type flexible resin adhesive to improve the curing degree and speed.
Preferably, the coating thickness of the photoresist is controlled to be 50-65um.
Preferably, the pre-controlling the environmental conditions specifically comprises: the ultraviolet irradiation intensity is 2800-3600mj/CM 2 The pressure of the illumination environment irradiated by the ultraviolet ray is controlled to be in a reduced pressure state lower than the atmospheric pressure, and the environment atmosphere is in a nitrogen or inert gas environment.
Specifically, the subsequent process can be started only when the fixed carrier and the wafer are firmly fixed, so that scrapping caused by the fact that the adhesive is not firmly fixed in the back grinding process is avoided, the adhesive is firm under normal conditions and is not easy to remove at the later stage, and time is required for complete solidification of the adhesive, so that the production rate is influenced; and the UV curing type flexible resin adhesive can be rapidly cured under the ultraviolet condition, the UV decomposition type flexible resin adhesive can be decomposed under the ultraviolet irradiation, so that the photoresist is convenient to separate, the speed of high adhesion or the speed of glue separation can be improved through the cooperation of the UV curing type flexible resin adhesive and the UV decomposition type flexible resin adhesive, and the production efficiency is improved.
Preferably, the wafer back grinding process specifically comprises rough grinding and fine grinding, the rough grinding is controlled respectively until the thickness of the wafer is not less than 160um, then the rough ground wafer is subjected to a laser radiation annealing process to remove a surface damage layer, the fine grinding is continued until the thickness of the wafer is not less than 55um after the surface damage layer is removed, and the wet etching process is carried out on the ground surface of the fine ground wafer to reduce the thickness by 1-5um.
Preferably, the rough grinding process conditions are specifically as follows: the rough grinding is controlled by adopting a grinding wheel with 400-800 meshes of abrasive materials, the pressure during the rough grinding is controlled to be 50-150kpa, the accurate grinding is controlled by adopting a grinding wheel with 2000-8000 meshes of abrasive materials, and the pressure during the accurate grinding is controlled to be 50-70kpa.
Specifically, in grinding process engineering such as back grinding, a grinding wheel with abrasive materials such as diamond attached to the surface or a grinding wheel is mainly adopted to directly rub the surface of a sample for thinning, but the rotating speed and the pressure in the thinning process can influence the surface stress effect, so that the local deformation of a wafer is easy to cause serious in the thinning process with gradually reduced rigidity, and the fineness of the abrasive materials can influence the flatness of the surface.
Preferably, the cooling liquid is added in the wafer back grinding process, the maximum processing temperature is controlled not to exceed 180 ℃, and the rotating speed of the grinding wheel is controlled to be 100-2500r/min, so that the wafer material deformation caused by high temperature is avoided.
Preferably, the laser radiation annealing process comprises the following specific steps: for the roughly ground wafer surface, pulse laser is used as a heat source, the frequency is controlled to be 0.8-1.2kHz, the pulse width is controlled to be 60-120ns, and the pulse width is controlled to be 3.5-6.5j/CM 2 The pulse energy is annealed. Because the rough grinding can form more obvious scratch depth and damage layer depth on the grinding surface, the part is easy to fall off in the later-stage fine grinding process, then large particles are formed to damage the surface of the wafer in the fine grinding process, and malignant influence is formed, so that the particles need to be removed in time through a laser radiation annealing process, and then the quality stability of the later-stage fine grinding is ensured.
Preferably, the wet etching process specifically comprises the following steps: selecting analytically pure dilute hydrochloric acid and phosphoric acid to prepare etching liquid, controlling the volume ratio of the analytically pure dilute hydrochloric acid to the phosphoric acid to be 1: 1/3-3, controlling the use environment temperature of the prepared etching liquid to be 18-23 ℃, and controlling the etching time to be not less than 45s.
Specifically, the purpose of wet etching is to remove the damaged layer on the surface after finish grinding, so as to reduce warpage; the etching liquid of the existing wet etching is mostly etched by bromine system etching liquid such as bromine system methyl alcohol, bromine water, HBR and the like or hydrochloric acid system etching liquid, but at present, the bromine system etching liquid still has defect structures such as etching pits, orange peel wrinkles and the like which are easy to leave on the surface of a wafer, and the surface of the wafer is rough, so the etching liquid is selected to be prepared because the etching rate and the intensity of dilute hydrochloric acid and phosphoric acid are moderate, and nitric acid of other hydrochloric acid systems has strong oxidizing property, the etching capability is too strong, the excessive etching is easy, the viscosity of sulfuric acid is high, and the surface passivation flow exchange capability is poor.
Compared with the prior art, the invention has the beneficial effects that:
the ultrathin wafer thinning process can play a role of supporting a rigid structure for thinning the wafer through the fixed carrier, and the surface of the wafer is protected from being influenced in the process by matching with the photoresist; the photoresist can realize rapid curing bonding or later stripping in the process, thereby being beneficial to improving the production efficiency; the surface of the wafer is processed by the laser radiation annealing process and the wet etching process in the back grinding process, so that the warping degree can be reduced, the flatness of the surface of the wafer can be better by the process method, the warping degree can be further reduced by optimizing the back grinding condition, the process method can be used for preparing the ultrathin wafer, and the process method is beneficial to improving the yield.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention details the above technical solution by the following embodiments:
example 1
An ultrathin wafer thinning process specifically comprises the following steps:
uniformly coating UV-curable flexible resin adhesive EX21-506 on the surface of the wafer and the surface of the carrier glass with flat and transparent surface by a spin coater, controlling the total thickness of the adhesive coating to be 50um, correspondingly attaching the carrier glass and the surface coated on the surface of the wafer, and controlling the ultraviolet irradiation intensity under the environmental condition to be 3200mj/CM 2 The pressure of the ultraviolet irradiation in the illumination environment is controlled to be 0.8 multiplied by 10 5 Pa, and the atmosphere is 80% nitrogen, thereby completing the fixation and bonding.
Fixedly mounting the fixedly bonded wafer on a grinding pad through carrier glass, enabling a grinding wheel to correspond to one surface which is not coated with photoresist, firstly carrying out coarse grinding, controlling the grain diameter of the grinding material of the coarse grinding wheel to be 600 meshes, controlling the pressure during coarse grinding to be 150kpa, controlling the rotating speed of the grinding wheel to be 2500r/min, synchronously applying deionized water at 18 ℃ as cooling liquid to control the coarse grinding temperature to be not more than 180 ℃, and coarsely grinding the thickness of the wafer to 175um; then, pulse laser is applied to the rough ground wafer surface as a heat source, the frequency is controlled to be 1.0kHz, the pulse width is 80ns, and the pulse width is 5j/CM 2 The pulse energy is used for annealing for 180s to remove the damaged layer, and the damaged layer which falls off after the treatment is removed by ultrasonic cleaning.
And then, continuously applying a grinding wheel rotating speed of 100r/min, controlling the grain diameter of the grinding material of the fine grinding wheel to be 8000 meshes, controlling the fine grinding pressure to be 50kpa, synchronously applying deionized water at 18 ℃ as cooling liquid to control the fine grinding temperature to be not more than 180 ℃, and finely grinding the thickness of the wafer to be 60um.
Selecting analytically pure diluted hydrochloric acid and phosphoric acid in a volume ratio of 1: 3 to prepare etching solution, controlling the etching environment temperature of the etching solution to be 18 ℃, etching for 120s to finish etching, removing the etching solution through CMP cleaning, then stripping carrier glass and removing UV-cured flexible resin adhesive EX21-506, attaching a slicing film, and finishing slicing according to requirements.
Example 2
An ultrathin wafer thinning process specifically comprises the following steps:
uniformly coating UV-curable flexible resin adhesive EX21-506 on the surface of the wafer and the surface of the carrier glass with flat and transparent surface by a spin coater, controlling the total thickness of the adhesive coating to be 50um, correspondingly attaching the carrier glass and the surface coated on the surface of the wafer, and controlling the ultraviolet irradiation intensity under the environmental condition to be 3200mj/CM 2 The pressure of the ultraviolet irradiation in the light environment is controlled to be 0.8 x 10 5 Pa, and the atmosphere is 80% nitrogen, thus completing the fixation and bonding.
Fixedly mounting the fixedly bonded wafer on a grinding pad through carrier glass, enabling a grinding wheel to correspond to one surface which is not coated with photoresist, firstly carrying out coarse grinding, controlling the grain diameter of the grinding material of the coarse grinding wheel to be 600 meshes, controlling the pressure during coarse grinding to be 150kpa, controlling the rotating speed of the grinding wheel to be 2500r/min, synchronously applying deionized water at 18 ℃ as cooling liquid to control the coarse grinding temperature to be not more than 180 ℃, and coarsely grinding the thickness of the wafer to 175um; then, pulse laser is applied to the rough ground wafer surface as a heat source, and the frequency is controlled to be 1.0kHz, the pulse width is controlled to be 80ns, and the pulse width is controlled to be 5j/CM 2 And (4) carrying out annealing treatment by pulse energy for 180s to remove the damaged layer, and cleaning by ultrasonic waves to remove the damaged layer peeled off after the treatment.
And then, continuously applying a grinding wheel rotating speed of 100r/min, controlling the grain diameter of the grinding material of the fine grinding wheel to be 8000 meshes, controlling the fine grinding pressure to be 70kpa, synchronously applying deionized water at 18 ℃ as cooling liquid to control the fine grinding temperature to be not more than 180 ℃, and finely grinding the thickness of the wafer to be 60um.
Selecting analytically pure diluted hydrochloric acid and phosphoric acid in a volume ratio of 1: 3 to prepare etching solution, controlling the etching environment temperature of the etching solution to be 18 ℃, etching for 120s to finish etching, removing the etching solution through CMP cleaning, then stripping carrier glass and removing UV-cured flexible resin adhesive EX21-506, attaching a slicing film, and finishing slicing according to requirements.
Example 3
An ultrathin wafer thinning process specifically comprises the following steps:
carrier with smooth and light-transmitting surface on wafer surface and surface through spin coaterUniformly coating UV curing type flexible resin adhesive EX21-506 on the surface of the glass, controlling the total thickness of the adhesive coating to be 50um, correspondingly attaching the carrier glass and the surface coated on the surface of the wafer, and controlling the ultraviolet irradiation intensity under the environmental condition to be 3200mj/CM 2 The pressure of the ultraviolet irradiation in the light environment is controlled to be 0.8 x 10 5 Pa, and the atmosphere is 80% nitrogen, thereby completing the fixation and bonding.
Fixedly mounting the fixedly bonded wafer on a grinding pad through carrier glass, enabling a grinding wheel to correspond to one surface which is not coated with photoresist, firstly carrying out coarse grinding, controlling the grain diameter of the grinding material of the coarse grinding wheel to be 600 meshes, controlling the pressure during coarse grinding to be 150kpa, controlling the rotating speed of the grinding wheel to be 2500r/min, synchronously applying deionized water at 18 ℃ as cooling liquid to control the coarse grinding temperature to be not more than 180 ℃, and coarsely grinding the thickness of the wafer to 175um; then, pulse laser is applied to the rough ground wafer surface as a heat source, and the frequency is controlled to be 1.0kHz, the pulse width is controlled to be 80ns, and the pulse width is controlled to be 5j/CM 2 The pulse energy is used for annealing for 180s to remove the damaged layer, and the damaged layer which falls off after the treatment is removed by ultrasonic cleaning.
And then, continuously applying the grinding wheel rotating speed of 100r/min, controlling the grain diameter of the grinding material of the fine grinding wheel to be 8000 meshes, controlling the fine grinding pressure to be 50kpa, synchronously applying deionized water at 18 ℃ as cooling liquid to control the fine grinding temperature to be not more than 180 ℃, and finely grinding the wafer to the thickness of 60um.
Selecting analytically pure dilute hydrochloric acid and phosphoric acid in a volume ratio of 3: 1 to prepare etching liquid, controlling the etching environment temperature of the etching liquid to be 18 ℃, completing etching within 120s, removing the etching liquid through CMP cleaning, then stripping carrier glass and removing UV curing type flexible resin adhesive EX21-506, attaching a slicing film, and completing slicing according to requirements.
Example 4
An ultrathin wafer thinning process specifically comprises the following steps:
uniformly coating UV-curable flexible resin adhesive EX21-506 on the surface of the wafer and the surface of the carrier glass with flat and transparent surface by a spin coater, controlling the total thickness of the adhesive coating to be 50um, correspondingly attaching the carrier glass and the surface coated on the surface of the wafer, and controlling the environment condition to control the ultraviolet rayIrradiation intensity of 3200mj/CM 2 The pressure of the ultraviolet irradiation in the light environment is controlled to be 0.8 x 10 5 Pa, and the atmosphere is 80% nitrogen, thus completing the fixation and bonding.
Fixedly mounting the fixedly bonded wafer on a grinding pad through carrier glass, enabling a grinding wheel to correspond to one surface which is not coated with photoresist, firstly performing coarse grinding, controlling the grain diameter of an abrasive of the coarse grinding wheel to be 600 meshes, controlling the pressure during coarse grinding to be 150kpa, controlling the rotation speed of the grinding wheel to be 2500r/min, synchronously applying deionized water at 18 ℃ as cooling liquid to control the coarse grinding temperature to be not more than 180 ℃, and coarsely grinding the thickness of the wafer to 175um; then, pulse laser is applied to the rough ground wafer surface as a heat source, and the frequency is controlled to be 1.0kHz, the pulse width is controlled to be 80ns, and the pulse width is controlled to be 5j/CM 2 The pulse energy is used for annealing for 180s to remove the damaged layer, and the damaged layer which falls off after the treatment is removed by ultrasonic cleaning.
And then, continuously applying the grinding wheel rotating speed of 100r/min, controlling the grain diameter of the grinding material of the fine grinding wheel to be 8000 meshes, controlling the fine grinding pressure to be 50kpa, synchronously applying deionized water at 18 ℃ as cooling liquid to control the fine grinding temperature to be not more than 180 ℃, and finely grinding the wafer to the thickness of 60um.
Selecting analytically pure dilute hydrochloric acid and phosphoric acid in a volume ratio of 1: 3 to prepare etching liquid, controlling the etching environment temperature of the etching liquid to be 18 ℃, completing etching within 90s, removing the etching liquid through CMP cleaning, then stripping carrier glass and removing UV curing type flexible resin adhesive EX21-506, attaching a slicing film, and completing slicing according to requirements.
Example 5
An ultrathin wafer thinning process specifically comprises the following steps:
uniformly coating UV-curing flexible resin adhesive EX21-506 on the surface of the wafer and the surface of the carrier glass with flat and transparent surface by a spin coater, controlling the total thickness of the adhesive coating to be 50um, correspondingly bonding the carrier glass and the surface coated on the surface of the wafer, and controlling the ultraviolet irradiation intensity under the environmental condition to be 3200mj/CM 2 The pressure of the ultraviolet irradiation in the light environment is controlled to be 0.8 x 10 5 Pa, and the atmosphere is 80% nitrogen, thus completing the fixation and bonding.
Fixedly mounting the fixedly bonded wafer on a grinding pad through carrier glass, enabling a grinding wheel to correspond to one surface which is not coated with photoresist, firstly performing coarse grinding, controlling the grain diameter of an abrasive of the coarse grinding wheel to be 600 meshes, controlling the pressure during coarse grinding to be 150kpa, controlling the rotation speed of the grinding wheel to be 2500r/min, synchronously applying deionized water at 18 ℃ as cooling liquid to control the coarse grinding temperature to be not more than 180 ℃, and coarsely grinding the thickness of the wafer to 175um; then, pulse laser is applied to the rough ground wafer surface as a heat source, and the frequency is controlled to be 1.0kHz, the pulse width is controlled to be 80ns, and the pulse width is controlled to be 5j/CM 2 The pulse energy is used for annealing for 180s to remove the damaged layer, and the damaged layer which falls off after the treatment is removed by ultrasonic cleaning.
And then continuously applying the grinding wheel rotating speed of 200r/min, controlling the grain diameter of the grinding material of the fine grinding wheel to be 8000 meshes, controlling the fine grinding pressure to be 50kpa, synchronously applying deionized water at 18 ℃ as cooling liquid to control the fine grinding temperature to be not more than 180 ℃, and finely grinding the wafer to the thickness of 60um.
Selecting analytically pure dilute hydrochloric acid and phosphoric acid in a volume ratio of 1: 3 to prepare etching solution, controlling the etching environment temperature of the etching solution to be 18 ℃, completing etching within 120s, removing the etching solution through CMP cleaning, then stripping carrier glass and removing UV curing type flexible resin adhesive EX21-506, attaching a slicing film, and completing slicing according to requirements.
Comparative example 1
Comparative example 1 differs from example 1 in that: in the comparative example, the laser radiation annealing process is not arranged, the rough grinding is directly carried out, and other conditions are the same.
Comparative example 2
Comparative example 2 differs from example 1 in that: the refining pressure in this comparative example was 150kpa, and the other conditions were the same.
Comparative example 3
Comparative example 3 differs from example 1 in that: in the comparative example, the rotation speed of the fine grinding wheel is 1600r/min, and other conditions are the same.
Comparative example 4
Comparative example 4 differs from example 1 in that: the etching time in this comparative example was 30s, and the other conditions were the same.
The thinned ultrathin wafers are prepared according to the thinning processes of the embodiments 1 to 5 and the comparative examples 1 to 4 respectively, and the TTV and the warpage of the ultrathin wafers are tested, wherein the TTV is the difference value between the maximum thickness and the minimum thickness in a plurality of thickness measurement values of the wafers in the thickness measurement, namely the total thickness change, and the warpage is higher when the warpage is larger to the bending degree, and the specific data are as follows:
| warping degree (mm) | TTV（um） | |
| Example 1 | 0.161 | 4.2 |
| Example 2 | 0.224 | 2.8 |
| Example 3 | 0.143 | 4.1 |
| Example 4 | 0.084 | 3.8 |
| Example 5 | 0.198 | 4.3 |
| Comparative example 1 | 1.896 | 3.3 |
| Comparative example 2 | 0.308 | 2.5 |
| Comparative example 3 | 2.051 | 4.9 |
| Comparative example 4 | 1.427 | 5.8 |
The data in the table above show that the etching time of the etching solution affects the warping degree of the etching solution, the longer the etching time is, the surface damage layer can be removed, and the removal of the damage layer by matching with the laser radiation annealing process is mainly used for further optimizing and reducing the warping degree, so that the flatness is better; the compounding ratio of the etching liquid has small influence on the etching effect, and has small difference on the etching effect; the factors mainly influencing warping degree are back grinding pressure and rotating speed; during fine grinding, the TTV can be reduced due to the increase of the pressure, namely the thickness uniformity is better, but the TTV gradually tends to be gentle along with the increase of the pressure, and the influence on the warping degree can be increased; the higher the rotation speed, the higher the warping degree is, and the lower the refining effect is, the higher the TTV value is, the lower the thickness uniformity is, and the embodiment 4 can be optimized by the data.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. An ultrathin wafer thinning process is characterized in that: the process specifically comprises the following steps: fixing and bonding the surface of the wafer and the fixed carrier through photoresist, controlling the thickness of bonding and curing to be uniform, fixing the fixed carrier on the grinding pad, continuously carrying out wet etching on the grinding surface after the wafer back grinding process, stripping the fixed carrier and removing the photoresist after a wafer back grinding damaged layer is eliminated, attaching a dicing film or a scribing film, and finishing dicing according to the requirement.
2. The ultra-thin wafer thinning process of claim 1, wherein: the fixed carrier adopts a transparent carrier plate or carrier glass with a smooth and transparent surface, and the photoresist adopts any one or more of UV curing type flexible resin adhesive or UV decomposition type flexible resin adhesive.
3. The ultra-thin wafer thinning process of claim 2, wherein: the specific process steps of the fixed bonding of the photoresist are as follows: respectively and uniformly coating UV curing type flexible resin adhesive or UV decomposition type flexible resin adhesive on the surface of the wafer or the surface of the fixed carrier corresponding to the surface of the wafer through a spin coater, correspondingly attaching the fixed carrier and the surface of the wafer coated with the photoresist, and controlling environmental conditions in advance to enable the UV curing type flexible resin adhesive to improve the curing degree and speed.
4. The ultra-thin wafer thinning process according to claim 3, wherein: and controlling the coating thickness of the photoresist to be 50-65um.
5. The ultra-thin wafer thinning process of claim 3, wherein: the pre-controlling the environmental conditions specifically comprises: the ultraviolet irradiation intensity is 2800-3600mj/CM 2 Controlling the pressure of the illumination environment irradiated by ultraviolet rays to be in a reduced pressure state lower than the atmospheric pressure, and the environmentThe atmosphere is in a nitrogen or inert gas environment.
6. The ultra-thin wafer thinning process of claim 1, wherein: the wafer back grinding process specifically comprises coarse grinding and fine grinding, wherein the coarse grinding is respectively controlled until the thickness of the wafer is not less than 160um, then the surface damage layer of the wafer after the coarse grinding is removed by using a laser radiation annealing process, the fine grinding is continuously carried out until the thickness of the wafer is not less than 55um after the surface damage layer is removed, and the thickness of the ground surface of the wafer after the fine grinding is reduced by 1-5um by using a wet etching process.
7. The ultra-thin wafer thinning process of claim 6, wherein: the rough grinding process conditions are as follows: the rough grinding is controlled by adopting a grinding wheel with 400-800 meshes of abrasive materials, the pressure during the rough grinding is controlled to be 50-150kpa, the accurate grinding is controlled by adopting a grinding wheel with 2000-8000 meshes of abrasive materials, and the pressure during the accurate grinding is controlled to be 50-70kpa.
8. The ultra-thin wafer thinning process according to claim 6, wherein: and cooling liquid is added in the process of the wafer back grinding process, the maximum processing temperature is controlled not to exceed 180 ℃, and the rotating speed of the grinding wheel is controlled to be 100-2500r/min.
9. The ultra-thin wafer thinning process of claim 6, wherein: the laser radiation annealing process comprises the following specific steps: for the roughly ground wafer surface, pulse laser is used as a heat source, the frequency is controlled to be 0.8-1.2kHz, the pulse width is controlled to be 60-120ns, and the pulse width is controlled to be 3.5-6.5j/CM 2 And annealing by pulse energy.
10. The ultra-thin wafer thinning process of claim 6, wherein: the wet etching process comprises the following specific steps: selecting analytically pure dilute hydrochloric acid and phosphoric acid to prepare etching liquid, controlling the volume ratio of the analytically pure dilute hydrochloric acid to the phosphoric acid to be 1: 1/3-3, controlling the use environment temperature of the prepared etching liquid to be 18-23 ℃, and controlling the etching time to be not less than 45s.
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