CN112053939B - Wafer bonding method - Google Patents
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- CN112053939B CN112053939B CN202010955641.8A CN202010955641A CN112053939B CN 112053939 B CN112053939 B CN 112053939B CN 202010955641 A CN202010955641 A CN 202010955641A CN 112053939 B CN112053939 B CN 112053939B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/185—Joining of semiconductor bodies for junction formation
- H01L21/187—Joining of semiconductor bodies for junction formation by direct bonding
Abstract
The invention provides a wafer bonding method, which comprises the following steps: providing a first wafer and a second wafer; activating the first surface of the first wafer and the second surface of the second wafer by adopting pulse bias plasma, so that Si dangling bonds are formed between the first surface and the second surface; performing hydrophilic treatment on the first wafer and the second wafer after the activation treatment to form silicon hydroxyl bonds on the first surface and the second surface; attaching the first wafer and the second wafer after hydrophilic treatment to complete the pre-bonding of the first wafer and the second wafer; and annealing the pre-bonded first wafer and the pre-bonded second wafer to complete bonding. The method can be used for attaching without damaging the wafer, so that the annealed bonded wafer has higher bonding energy, and the reliability of the device is improved.
Description
Technical Field
The invention relates to a wafer bonding method, and belongs to the technical field of semiconductor manufacturing.
Background
Wafer-to-wafer bonding is an emerging technology in the field of semiconductor manufacturing that enables polished semiconductor wafers to be bonded together without the use of adhesives. The direct bonding between the wafers is realized by utilizing the atomic bonding force of the surfaces of the two wafers, and treating the atomic bonding force to ensure that the atoms on the surfaces of the two wafers react to generate covalent bonding and realize certain connection strength.
Usually, plasma is used for bombarding the surface of a wafer, so that the surface of the wafer generates a physical and chemical double reaction, pollutants on the surface of the wafer are changed into particles or gas, and the pollutants are exhausted by vacuum pumping, so that the purposes of cleaning and activating the surface are achieved; meanwhile, a highly irregular porous structure is generated on the surface, the diffusion of water molecules on a bonding interface is improved, hydroxyl groups are formed on the surface, the number of hydroxyl bonds is more, and the bonding force of the wafer is higher after the subsequent annealing process is finished.
Disclosure of Invention
The invention aims to provide a wafer bonding method, which is used for activating a wafer through pulse bias plasma, so that the activation degree of the surface of the wafer is improved, and the bonding force of the bonded wafer is improved.
According to an aspect of the present invention, there is provided a wafer bonding method, including:
providing a first wafer and a second wafer;
activating the first surface of the first wafer and the second surface of the second wafer by adopting pulse bias plasma, so that Si dangling bonds are formed between the first surface and the second surface;
performing hydrophilic treatment on the first wafer and the second wafer after the activation treatment to form silicon hydroxyl bonds on the first surface and the second surface;
attaching the first wafer and the second wafer after hydrophilic treatment to complete the pre-bonding of the first wafer and the second wafer;
and annealing the pre-bonded first wafer and the pre-bonded second wafer to complete bonding.
Preferably, the pulse bias voltage when the pulse bias plasma is formed is 300 to 12000V.
The discharge power for forming the pulsed bias plasma is 10 to 450W.
The gas forming the pulsed bias plasma is one or more of nitrogen, oxygen and argon.
The reagent for hydrophilic treatment is ammonia water, a mixed solution of hydrogen peroxide and water, or deionized water in a mass ratio of (1.
The flow rate of the hydrophilic treatment reagent is 0.5-2L/min.
The temperature of the hydrophilic treatment is 23-65 ℃.
The annealing temperature of the annealing treatment is 100-200 ℃, and the annealing time is 1-2 hours.
Preferably, the annealing treatment is performed under normal pressure.
According to the method, the activation step of the plasma by applying the pulse bias is combined with the hydrophilic treatment step, so that the reactivity of the surface of the wafer is improved, and the bonding quality is improved.
Drawings
Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:
FIG. 1 schematically illustrates a process flow diagram of a wafer bonding method according to the present invention;
fig. 2 schematically shows a process flow diagram of a wafer bonding method according to embodiment 1 of the present invention;
fig. 3 schematically shows a process flow diagram of a wafer bonding method according to embodiment 2 of the present invention.
Detailed Description
As shown in fig. 1, the wafer bonding method according to the present invention includes the following steps:
step S1: providing a first wafer and a second wafer;
step S2: activating the first surface of the first wafer and the second surface of the second wafer by adopting pulse bias plasma, so that Si dangling bonds are formed between the first surface and the second surface;
and step S3: performing hydrophilic treatment on the first wafer and the second wafer after the activation treatment to form silicon hydroxyl bonds on the first surface and the second surface;
and step S4: attaching the first wafer and the second wafer after hydrophilic treatment to complete the pre-bonding of the first wafer and the second wafer;
step S5: and annealing the pre-bonded first wafer and the pre-bonded second wafer to complete bonding.
The first wafer and the second wafer used in the invention can be polished or cleaned in advance to improve the flatness and cleanliness of the surfaces of the wafers to be bonded, which is beneficial to improving the bonding effect and reducing the bonding defects.
In step S2 of the above method, pulsed bias plasma is used to activate the surfaces to be bonded of the two wafers. And (3) bombarding the silicon oxide layer on the surface of the wafer by applying the plasma with pulse bias voltage, breaking Si-O bonds in the silicon oxide layer, and forming Si-dangling bonds.
Compared with the conventional plasma activation method, the method applies radio frequency pulse bias to the plasma while respectively performing surface activation treatment on two wafers by using the plasma, the radio frequency bias establishes a radio frequency sheath layer between the plasma and the bias, the potential of the bias electrode oscillates in high frequency by taking a certain average potential as a center, so that the electric field of the sheath layer is also changed violently, and the potential of the bias electrode is lower than the space potential of the plasma, so that ions are accelerated when passing through the radio frequency sheath layer to generate a stronger ion bombardment effect. Meanwhile, the potential of the bias electrode is modulated in time, the electrode is in a bias state only in part of the time in one pulse period, and under the condition that the average power is the same, the ion energy of the incident substrate is larger when the excitation power supply is started, so that the intensity and the time of ion bombardment can be adjusted. Therefore, more Si-dangling bonds can be obtained during the activation of the wafer surface, then silicon hydroxyl bonds are formed, and the number of Si-O-Si bonds is increased after annealing treatment, so that the bonding energy is enhanced.
In one embodiment, the pulsed bias plasma is formed at a pulsed bias of 300 to 12000V, preferably 800 to 10000V, more preferably 1500 to 8000V, for example 2000 to 6000V; the discharge power is 10 to 450W, preferably 50 to 380W, more preferably 100 to 300W, for example 150 to 250W.
In the method of the present invention, the gas forming the pulsed bias plasma may be one or more of nitrogen, oxygen, or argon, and may be nitrogen, for example.
In step S2, the air pressure of the process can be 1-10 × 10 -2 Pa, preferably 3 to 7X 10 -2 Pa, e.g. 5X 10 - 2 Pa. In addition, the plasma treatment time may be 20-40s.
In the hydrophilic treatment process of step S3, the silicon dangling bonds on the wafer surface treated by the pulsed bias plasma adsorb hydroxyl groups of the hydrophilic treatment agent to form silicon hydroxyl bonds, so that the hydrophilicity of the wafer surface is significantly enhanced.
Specifically, the hydrophilic treatment agent usable in the present invention may be ammonia water, a mixed solution of hydrogen peroxide and water (RCA solution), or deionized water in a mass ratio of (1.
The RCA solution is formed by mixing 25 to 28% (mass percent) of an ammonia solution, 25 to 30% (mass percent) of a hydrogen peroxide solution, and water in a mass ratio of (1. The method also has the effects of removing microparticles and a part of metal ions attached to the wafer, and activating the surface layer of the silicon by using weak alkalinity of ammonia water. The silicon-hydroxyl bond content on the surface of the wafer treated by the mixed solution is high, the wafer is effectively activated, and the hydrophilicity is improved.
In the method, because the activation degree of the surface of the wafer treated by the pulse bias plasma is high, namely the silicon dangling bond content is high, the deionized water with low hydroxyl content can be used for carrying out effective hydrophilic treatment, and a large number of silicon hydroxyl bonds can be formed on the surface of the wafer to provide sufficient hydrophilicity. Meanwhile, the deionized water can also effectively remove the microparticles on the surface of the wafer.
In step S4, before the annealing process, the wafer subjected to hydrophilic treatment is aligned and attached in a bonding apparatus, and pre-bonded. After the pulse bias plasma treatment and the hydrophilic treatment, the surfaces of the wafers have abundant silicon hydroxyl bonds, and the two wafers attract each other to form hydrogen bonds when approaching, so that the wafers have certain bonding force.
In step S5, the annealing temperature may be controlled to 100 to 200 ℃ for 1 to 2 hours, and the annealing is performed in an atmospheric atmosphere at normal pressure.
In the method according to the invention, the bonding strength between the two bonded wafers is more than 2.5J/m 2 。
Further, annealing the pre-bonded wafer in an annealing device to perform dehydration condensation between silicon hydroxyl bonds to form Si-O-Si bonds, thereby forming a final bonded wafer:
Si-OH+Si-OH→Si-O-Si+H 2 O。
according to the wafer bonding method, the high-energy plasma particles are obtained by using the pulse bias voltage, the ion kinetic energy is increased, the bombardment effect on the surface of the wafer is formed, the number of dangling bonds on the surface of the wafer is obviously increased, the reactivity of the surface of the wafer can be further improved, and the bonding quality is improved.
Examples
Example 1
Referring to fig. 2, the steps of the wafer bonding method are as follows:
the first step is as follows: two silicon wafers are selected, and a plurality of bonding areas are respectively arranged on the two silicon wafers.
The second step is that: and respectively carrying out pulse bias plasma activation treatment on the surfaces of the two wafers. The system was pumped down to 1X 10 -4 Opening the nitrogen gas inlet system after Pa, raising the gas pressure back to 60Pa, circulating twice air pumping and discharging to ensure the environment of the chamber, and then maintaining the nitrogen gas pressure at 1-10 multiplied by 10 -2 Pa, discharge was resumed with a discharge power of 50W, and a pulse bias voltage was adjusted to 1000V. The time for the pulsed bias plasma activation treatment was 20 seconds. Due to the auxiliary action of the bias voltage, ions are accelerated when passing through the radio frequency sheath layer to generate an ion bombardment effect, and the treatment effect is enhanced.
The third step: and carrying out hydrophilic treatment. And (2) respectively performing a cleaning process on the two wafers after the plasma activation, cleaning the surfaces of the wafers by using deionized water, wherein a hydrophilic treatment reagent is an RCA solution (a mixed solution of ammonia water, hydrogen peroxide and water in a ratio of 1. And then, carrying out nitrogen blow drying on the wafer.
The fourth step: and carrying out wafer pre-bonding. And loading one wafer to the upper chuck, loading the other wafer to the lower chuck, aligning the regions to be bonded of the two wafers through the vision system and the alignment system, bonding the two wafers after alignment, and performing pre-bonding.
The fifth step: and annealing the pre-bonded wafer pair. And (3) conveying the wafer pairs subjected to pre-bonding into an annealing furnace, annealing at 200 ℃ for 1 hour under normal pressure, and obtaining the final bonded wafer.
The bonding strength of the bonded wafer was measured to be 3J/m 2 。
Example 2
Referring to fig. 3, the steps of the wafer bonding method are as follows:
the first step is as follows: two silicon wafers are selected, and a plurality of bonding areas are respectively arranged on the two silicon wafers.
The second step is that: and respectively carrying out pulse bias plasma activation treatment on the surfaces of the two wafers. The system was pumped down to 1X 10 -4 Opening the nitrogen gas inlet system after Pa, raising the gas pressure back to 60Pa, circulating twice air pumping and discharging to ensure the environment of the chamber, and then maintaining the nitrogen gas pressure at 5-10 multiplied by 10 -2 Pa, discharge was resumed with a discharge power of 450W, and a pulse bias voltage was adjusted to 12000V. The time for the pulsed bias plasma activation treatment was 40 seconds. Due to the auxiliary action of the bias voltage, ions are accelerated when passing through the radio frequency sheath layer to generate an ion bombardment effect, and the treatment effect is enhanced.
The third step: and carrying out hydrophilic treatment. And respectively carrying out a cleaning process on the two wafers after the plasma activation, and cleaning the surfaces of the wafers by using deionized water, wherein the hydrophilic treatment reagent is deionized water, the temperature of the reagent is 65 ℃, and the flow rate is 2L/min. And then, carrying out nitrogen blow drying on the wafer.
The fourth step: and carrying out wafer pre-bonding. And loading one wafer to the upper chuck, loading the other wafer to the lower chuck, aligning the regions to be bonded of the two wafers through the vision system and the alignment system, attaching the two wafers after alignment, and performing pre-bonding.
The fifth step: and carrying out annealing treatment. And (3) conveying the wafer pair subjected to pre-bonding into an annealing furnace, annealing at 100 ℃ for 2 hours under normal pressure, and obtaining the final bonded wafer.
Detecting the bonding strength of the bonded wafer to be more than 2.5J/m 2 。
Comparative example 1
Wafer bonding was performed in the same manner as in example 1 except that the plasma activation treatment was performed under conditions such that no pulse bias voltage was applied, an alternating voltage of 220V was applied, and a discharge power was 200W. Measured out ofThe bonding strength of the bonded wafer is 2J/m 2 。
Comparative example 2
Wafer bonding was performed in the same manner as in example 2 except that the plasma activation treatment was performed under conditions such that no pulse bias voltage was applied, an alternating voltage of 220V was applied, and a discharge power was 200W. The bonding strength of the bonded wafer was measured to be 1.5J/m 2 。
As can be seen from the above examples 1 and 2 and comparative examples 1 and 2, according to the method of the present invention, the bonding strength between wafers is improved by the pulsed bias plasma treatment, the bonding effect is significantly enhanced, and particularly, the improvement of the bonding effect is more significant when the hydrophilic treatment is performed with deionized water having a small hydroxyl group content.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims (8)
1. A wafer bonding method, comprising:
providing a first wafer and a second wafer;
applying radio frequency pulse bias voltage to the plasma while activating the first surface of the first wafer and the second surface of the second wafer by using the plasma, setting the potential of a bias electrode to oscillate by taking an average potential as a center, wherein the potential of the bias electrode is lower than the space potential of the plasma, and the potential of the bias electrode enables the electrode to be in a bias state in a part of time in a pulse period so that the first surface and the second surface form a Si dangling bond;
performing hydrophilic treatment on the first wafer and the second wafer after the activation treatment to form silicon hydroxyl bonds on the first surface and the second surface; the hydrophilic treatment reagent is ammonia water, a mixed solution of hydrogen peroxide and water, or deionized water, wherein the mixed solution is formed by mixing 25-28% by mass of an ammonia water solution, 25-30% by mass of a hydrogen peroxide solution and water in a mass ratio of (1;
attaching the first wafer and the second wafer after hydrophilic treatment to complete pre-bonding;
and annealing the pre-bonded first wafer and the pre-bonded second wafer to complete bonding.
2. The wafer bonding method according to claim 1, wherein the pulsed bias plasma is formed at a pulsed bias voltage of 300 to 12000V.
3. The wafer bonding method according to claim 1, wherein the discharge power when the pulsed bias plasma is formed is 10 to 450W.
4. The wafer bonding method according to claim 1, wherein the gas forming the pulsed bias plasma is one or more of nitrogen, oxygen, and argon.
5. The wafer bonding method according to claim 1, wherein the flow rate of the hydrophilic treatment reagent is 0.5 to 2L/min.
6. The wafer bonding method according to claim 1, wherein the temperature of the hydrophilic treatment is 23 ℃ to 65 ℃.
7. The wafer bonding method according to claim 1, wherein the annealing temperature of the annealing treatment is 100 to 200 ℃ and the annealing time is 1 to 2 hours.
8. The wafer bonding method according to claim 1, wherein the annealing treatment is performed under normal pressure.
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| CN113345803A (en) * | 2021-05-31 | 2021-09-03 | 长江存储科技有限责任公司 | Wafer bonding method |
| CN113745095A (en) * | 2021-09-03 | 2021-12-03 | 湖北三维半导体集成创新中心有限责任公司 | Method for cleaning metal oxide on bonding surface |
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| CN107633997B (en) * | 2017-08-10 | 2019-01-29 | 长江存储科技有限责任公司 | A kind of wafer bonding method |
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