CN115928034A - Thin film deposition method and thin film deposition apparatus - Google Patents
Thin film deposition method and thin film deposition apparatus Download PDFInfo
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Abstract
The present invention provides a thin film deposition method and a thin film deposition apparatus, including: introducing reducing gas into the pre-cleaning chamber to perform reduction reaction with the oxide layer on the surface to be deposited of the wafer to remove the oxide layer; depositing a first metal layer which can be mutually dissolved with the wafer on the surface to be deposited of the wafer by adopting a first magnetron sputtering method in a first deposition chamber; and obtaining the mutual soluble structure of the first metal layer and the wafer by controlling the temperature of the base adopted by the first magnetron sputtering method. The film deposition method and the film deposition equipment provided by the invention can reduce the surface damage of the wafer, improve the mutual solubility effect of metal and the wafer, and obtain a more ideal mutual solubility structure, thereby reducing the contact resistance of a chip, improving the product performance, simplifying the process steps and improving the productivity.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a thin film deposition method and thin film deposition equipment.
Background
The backside metallization process plays an important role in the performance of the power device chip. Currently, the backside metallization process applied to the mainstream of an IGBT (Insulated Gate Bipolar Transistor) mainly deposits a stack of metals, such as a stack of aluminum/titanium/nickel vanadium/silver, by a magnetron sputtering process.
In the existing thin film deposition method, when a pre-cleaning step is performed on the back surface of a wafer (i.e., a silicon wafer), a natural oxide layer on the surface of the silicon wafer is removed by bombarding the back surface of the wafer with plasma, and then a magnetron sputtering deposition process of an aluminum metal layer is performed on the back surface of the wafer after the pre-cleaning, wherein a base used in the process has a temperature of room temperature (e.g., 20 ℃). And then, withdrawing the wafer subjected to aluminum metal deposition from the magnetron sputtering equipment, transferring the wafer into high-temperature annealing equipment to perform a high-temperature annealing process so as to obtain an aluminum-silicon mutual-soluble structure, and transferring the wafer into the magnetron sputtering equipment to perform titanium/nickel-vanadium/silver metal deposition, thereby completing the aluminum/titanium/nickel-vanadium/silver laminated back metallization process.
The above-described thin film deposition method inevitably has the following problems in practical use, namely:
firstly, because the natural oxide layer on the surface of the silicon substrate is removed by adopting a mode of bombarding the back surface of the wafer by plasma in the pre-cleaning step, the bombarding action on the wafer can activate atoms on the surface of the silicon wafer, so that abnormal silicon bump failure morphology as shown in fig. 1 is generated at the interface of the silicon wafer and aluminum metal, and a normal aluminum-silicon mutual-soluble tissue cannot be formed, thereby causing the contact resistance of the prepared chip to be higher and the product performance to be reduced.
Secondly, the plasma adopted to bombard the back of the wafer in the pre-cleaning step is easy to damage the surface of the silicon wafer to a certain extent, and the aluminum-silicon mutual dissolving effect is influenced, so that the product performance is influenced.
Thirdly, the wafer needs to be withdrawn from the magnetron sputtering equipment, and is transferred into the annealing equipment to be subjected to the annealing process, and then returns to the magnetron sputtering equipment again to be subjected to the titanium/nickel-vanadium/silver three-layer metal deposition, so that the process steps are complicated, the productivity is influenced, the aluminum metal layer is easily oxidized when exposed in the atmospheric environment, the bonding force between aluminum and titanium is also influenced to a certain extent, and the product yield is low.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art, and provides a film deposition method and film deposition equipment, which can reduce the surface damage of a wafer, improve the mutual dissolving effect of metal and the wafer, and obtain an ideal mutual dissolving structure, thereby reducing the contact resistance of a chip, improving the product performance, simplifying the process steps and improving the productivity.
To achieve the object of the present invention, there is provided a thin film deposition method including:
introducing reducing gas into the pre-cleaning chamber to perform reduction reaction with the oxide layer on the surface to be deposited of the wafer to remove the oxide layer;
depositing a first metal layer which can be mutually dissolved with the wafer on the surface to be deposited of the wafer by adopting a first magnetron sputtering method in a first deposition chamber;
and obtaining a mutual soluble structure of the first metal layer and the wafer by controlling the temperature of a base adopted by the first magnetron sputtering method.
Optionally, the temperature of the base in the first magnetron sputtering method is controlled to be greater than or equal to 300 ℃ and less than or equal to 380 ℃.
Optionally, after depositing, in the first deposition chamber, a first metal layer that is miscible with the wafer on the surface to be deposited of the wafer by using a first magnetron sputtering method, the thin film deposition method further includes:
depositing a second metal layer on the wafer deposited with the first metal layer in a second deposition chamber by adopting a second magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the second magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the second metal layer at the first wafer so as to promote the mutual solubility of the first metal layer and the wafer.
Optionally, after depositing a second metal layer on the wafer deposited with the first metal layer by using a second magnetron sputtering method in the second deposition chamber, the film is deposited
The product method further comprises:
depositing a third metal layer on the wafer deposited with the second metal layer in a third deposition chamber by adopting a third magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the third magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the third metal layer at the second wafer so as to promote the mutual solubility of the first metal layer and the wafer.
Optionally, after depositing a third metal layer on the wafer deposited with the second metal layer by using a third magnetron sputtering method in the third deposition chamber, the thin film deposition method further includes:
and cooling the wafer in a cooling chamber, and controlling the temperature of the wafer at a third wafer temperature so as to promote mutual solubility of the first metal layer and the wafer.
Optionally, after the wafer is cooled in the cooling chamber, the thin film deposition method further includes:
depositing a fourth metal layer on the wafer deposited with the third metal layer in a fourth deposition chamber by adopting a fourth magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the fourth magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the fourth metal layer is finished at the fourth wafer so as to promote the mutual solubility of the first metal layer and the wafer.
Optionally, the temperature of the first wafer is greater than or equal to 250 ℃ and less than or equal to 300 ℃; the temperature of the second wafer is more than or equal to 300 ℃ and less than or equal to 330 ℃; the temperature of the third wafer is more than or equal to 210 ℃ and less than or equal to 240 ℃; the temperature of the fourth wafer is more than or equal to 300 ℃ and less than or equal to 330 ℃.
Optionally, controlling the temperature of the base in the second magnetron sputtering method to be lower than 0 ℃; controlling the temperature of the base in the third magnetron sputtering method to be lower than 0 ℃; and controlling the temperature of the base in the fourth magnetron sputtering method to be lower than 0 ℃.
Optionally, the wafer is made of silicon; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel vanadium; the fourth metal layer is silver.
As another technical solution, the present invention further provides a thin film deposition apparatus applied to the thin film deposition method provided by the present invention, the thin film deposition apparatus includes the pre-cleaning chamber and the first deposition chamber, wherein a pedestal and a deposition ring disposed around the pedestal are disposed in the first deposition chamber, the deposition ring has an annular support portion, and a top end of the annular support portion is higher than an upper surface of the pedestal and is used for supporting a lower surface edge region of the wafer; a susceptor in the first deposition chamber has a heating function;
and a cooling channel for conveying a cooling medium is arranged in the deposition ring, and an inlet and an outlet of the cooling channel are respectively connected with a cooling circulation system through two flexible pipelines.
Optionally, the thin film deposition apparatus further includes a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber, and a loading and unloading chamber, or further includes a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a loading and unloading chamber having a cooling function; wherein the susceptors in the second deposition chamber, the third deposition chamber and the fourth deposition chamber have a cooling function.
The invention has the following beneficial effects:
according to the technical scheme of the film deposition method and the film deposition equipment, the reduction pre-cleaning technology is adopted, namely, reducing gas is introduced into the pre-cleaning chamber to perform reduction reaction with the oxide layer on the surface to be deposited of the wafer to remove the oxide layer on the surface to be deposited of the wafer, so that the oxide layer can be removed to the lowest damage degree, atoms on the surface of the silicon wafer are prevented from being activated, and abnormal silicon bulge failure appearance can be avoided; moreover, when the first metal layer which can be mutually dissolved with the wafer is deposited on the surface to be deposited of the wafer by adopting the first magnetron sputtering method, the mutual dissolving structure of the first metal layer and the wafer can be obtained by controlling the temperature of the base, so that the annealing process in the prior art can be omitted, the wafer does not need to be transmitted between the magnetron sputtering equipment and the annealing equipment, the process steps can be simplified, the capacity can be improved, the first metal layer can be prevented from being exposed in the atmospheric environment, the bonding force between metals can be ensured, and the product performance can be improved.
Drawings
FIG. 1 is an electron microscope scanning image of abnormal silicon bump failure morphology generated at the interface of a silicon wafer and aluminum metal in the prior art;
FIG. 2 is a block flow diagram of a thin film deposition method according to an embodiment of the present invention;
FIG. 3 is another block flow diagram of a thin film deposition method according to an embodiment of the present invention;
fig. 4 is an electron microscope scan of the interface between the silicon wafer and the aluminum metal obtained after the completion of steps S1 to S6 of the thin film deposition method according to the embodiment of the present invention;
fig. 5 is a schematic structural diagram of a first deposition chamber of the thin film deposition apparatus according to an embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the following describes the thin film deposition method and thin film deposition apparatus provided by the present invention in detail with reference to the accompanying drawings.
Referring to fig. 2, the thin film deposition method according to the embodiment of the present invention is applied to a backside metallization process, i.e., a metal stack, such as an al/ti/ni-v/ag stack, is deposited on the backside of a silicon wafer. The film deposition method comprises the following steps:
s1, introducing reducing gas into a pre-cleaning chamber to perform a reduction reaction with an oxide layer on a surface to be deposited of a wafer to remove the oxide layer;
the pre-cleaning chamber is used for pre-cleaning in the thin film deposition equipment.
In the step S1, a reduction precleaning technique without plasma is adopted, so that the oxide layer can be removed to the lowest extent of damage, and atoms on the surface of the silicon wafer are prevented from being activated, thereby preventing abnormal silicon bump failure morphology. The oxide layer is, for example, a native oxide layer on a silicon wafer.
Optionally, the temperature of the base in the first magnetron sputtering method is controlled to be greater than or equal to 300 ℃ and less than or equal to 380 ℃. By controlling the temperature of the susceptor within this range, the reducing gas is facilitated to undergo a reduction reaction with the oxide layer on the surface of the wafer to be deposited.
Alternatively, the reducing gas comprises, for example, hydrogen. The chamber pressure is 3mT or more and 4mT or less.
For the back side metallization process, the surface of the wafer to be deposited is the back side of the wafer, i.e., the front side of the wafer is opposite to the surface of the susceptor for carrying the wafer. Of course, in practical applications, the surface to be deposited may also be a front surface of a wafer, and this is not particularly limited by the embodiment of the present invention.
Optionally, before performing the step S1, the thin film deposition method may further include:
s01, cleaning the surface of the wafer to be deposited;
s02, baking the wafer to dry the wafer.
Optionally, the baking temperature is greater than or equal to 150 ℃ and less than or equal to 200 ℃.
S2, depositing a first metal layer capable of being mutually soluble with the wafer on the surface to be deposited of the wafer by adopting a first magnetron sputtering method in a first deposition chamber;
the first deposition chamber is a magnetron sputtering chamber for depositing a first metal layer in a thin film deposition apparatus, for example, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the pre-cleaning chamber, a first deposition chamber, and a Load-lock chamber (Load-lock). The pre-clean chamber, the first deposition chamber and the load lock chamber are surrounded by a transfer chamber, and a robot in the transfer chamber is capable of transferring wafers among the pre-clean chamber, the first deposition chamber and the load lock chamber. A liftable base is arranged in the first deposition chamber and used for bearing the wafer, and the base is integrated with a heating device so as to heat the wafer. Furthermore, a target (the material is the same as that of the first metal layer) is arranged on the top of the first deposition chamber, and the target is electrically connected with a sputtering power supply, and the sputtering power supply is used for applying sputtering power to the target so as to excite the sputtering gas in the first deposition chamber to form plasma. The sputtering power supply is, for example, a dc power supply. The first magnetron sputtering method includes: and introducing a process gas (such as argon) into the first deposition chamber, starting a sputtering power supply to excite the process gas to form plasma, and bombarding the target by the plasma so that target atoms escape from the surface of the target and are deposited on the wafer to form a first metal layer.
In the step S2, the mutual soluble structure of the first metal layer and the wafer is obtained by controlling the temperature of the substrate used in the first magnetron sputtering method.
When the step S2 is adopted, that is, when the first magnetron sputtering method is adopted to deposit the first metal layer capable of being dissolved in the wafer on the surface to be deposited of the wafer, the mutual dissolution structure of the first metal layer and the wafer can be obtained by controlling the temperature of the base, that is, when the first metal layer is deposited, the wafer is heated by controlling the temperature of the base, the temperature of the wafer can be increased, the mutual dissolution of the first metal layer and the wafer can be promoted, so as to obtain the mutual dissolution structure of the first metal layer and the wafer, the existence of the mutual dissolution structure can reduce the contact resistance of the chip, and improve the product performance. Therefore, the thin film deposition method provided by the embodiment of the invention can save the annealing process in the prior art, so that the wafer does not need to be transmitted between the thin film deposition equipment and the annealing equipment, the process steps can be simplified, the productivity is improved, the first metal layer can be prevented from being exposed in the atmospheric environment, the bonding force between metals can be ensured, and the product performance can be improved.
In some optional embodiments, in the step S2, the base temperature adopted by the first magnetron sputtering method is greater than or equal to 300 ℃ and less than or equal to 380 ℃, and by setting the base temperature within the range, the mutual solubility of the first metal layer and the wafer can be promoted, so as to obtain a more ideal mutual solubility structure; and the higher base temperature is adopted, so that the annealing process in the prior art can be replaced, a foundation is provided for enabling the wafer temperature to reach a reasonable range during the subsequent deposition of laminated metal, the wafer temperature is always controlled within the temperature range capable of promoting the mutual solubility of the first metal layer and the wafer after the deposition of all the metal layers is finished, the process steps are further simplified, and the productivity is improved.
In some optional embodiments, referring to fig. 3, the thin film deposition method provided in the embodiment of the present invention may be applied to deposit a stack of metal layers on a wafer, that is, after the deposition of the first metal layer is completed in step S2, the thin film deposition method further includes:
s3, depositing a second metal layer on the wafer deposited with the first metal layer in a second deposition chamber by adopting a second magnetron sputtering method;
the second deposition chamber is a magnetron sputtering chamber for depositing a second metal layer in a thin film deposition apparatus, for example, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, and a load-unload chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, and the load-unload chamber are surrounded by the transfer chamber, and a robot in the transfer chamber can transfer wafers among the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, and the load-unload chamber. The second deposition chamber has substantially the same structure as the first deposition chamber, and the material of the target and the structure and function of the pedestal are different, specifically, the material of the target in the second deposition chamber is the same as the second metal layer, and the pedestal in the second deposition chamber is integrated with a cooling device for cooling the wafer. The second magnetron sputtering method is the same as the first magnetron sputtering method, and is used for forming the second metal layer.
The wafer can be cooled by controlling the temperature of the base adopted by the second magnetron sputtering method, and the temperature of the first wafer after the deposition of the second metal layer is controlled, so that the mutual solubility of the first metal layer and the wafer is promoted. That is, by controlling the wafer temperature to the first wafer temperature, it is beneficial to further increase the generation of the miscible structure. Optionally, the temperature of the first wafer is greater than or equal to 250 ℃ and less than or equal to 300 ℃; optionally, the temperature of the susceptor is lower than 0 ℃ to cool the wafer. When the second metal layer is deposited by the second magnetron sputtering method, the wafer temperature may be increased due to the higher energy of the particles and the longer deposition time compared to the first metal layer deposited by the first magnetron sputtering method, and in this case, the wafer needs to be cooled by the base to control the wafer temperature at the first wafer temperature.
In some optional embodiments, referring to fig. 3, after the deposition of the second metal layer is completed in step S3, the thin film deposition method further includes:
s4, depositing a third metal layer on the wafer deposited with the second metal layer in a third deposition chamber by adopting a third magnetron sputtering method;
the third deposition chamber is a magnetron sputtering chamber for depositing a third metal layer in a thin film deposition device, for example, the thin film deposition device includes, but is not limited to, a transfer chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, and a loading and unloading chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, and the loading and unloading chamber surround the transfer chamber, and a robot in the transfer chamber can transfer wafers among the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, and the loading and unloading chamber. The third deposition chamber has substantially the same structure as the second deposition chamber, and the material of the target is different, that is, the material of the target in the third deposition chamber is the same as that of the third metal layer. The third magnetron sputtering method is the same as the second magnetron sputtering method, and is used for forming a third metal layer. In addition, the base in the third deposition chamber is integrated with a cooling device for cooling the wafer.
And controlling the temperature of the second wafer after the deposition of the third metal layer is finished by controlling the temperature of the base adopted by the third magnetron sputtering method so as to promote the mutual solubility of the first metal layer and the wafer. That is, by controlling the wafer temperature to the second wafer temperature, it is beneficial to further increase the generation of the miscible structure. Optionally, the second wafer temperature is greater than or equal to 300 ℃ and less than or equal to 330 ℃. Optionally, the temperature of the susceptor is lower than 0 ℃ to cool the wafer. When the third metal layer is deposited by the third magnetron sputtering method, the wafer temperature may be increased due to the higher energy of the particles and the longer deposition time compared to the first metal layer deposited by the first magnetron sputtering method, and in this case, the wafer needs to be cooled by the base to control the wafer temperature at the second wafer temperature.
After depositing a metal such as nickel vanadium, the wafer needs to be cooled to meet the requirements of the subsequent process due to the high temperature of the wafer. In view of this, in some optional embodiments, after the deposition of the third metal layer is completed in step S4, referring to fig. 3, the thin film deposition method further includes:
and S5, cooling the wafer in the cooling chamber, and controlling the temperature of the wafer at the temperature of a third wafer so as to promote the mutual solubility of the first metal layer and the wafer.
By controlling the temperature of the wafer at the temperature of the third wafer, the generation of the mutual soluble structure can be further increased on the premise of meeting the requirement of the deposition process of the fourth metal layer. Optionally, the temperature of the third wafer is greater than or equal to 210 ℃ and less than or equal to 240 ℃.
Alternatively, the cooling chamber may be a chamber separately disposed in the thin film deposition apparatus, or may be a Load-lock (Load-lock) integrated with a cooling function, for example, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, a cooling chamber, and a Load-lock chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the cooling chamber, and the Load-lock chamber are surrounded by the transfer chamber, and a robot in the transfer chamber can transfer the wafer between the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the cooling chamber, and the Load-lock chamber. Alternatively, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the above-described pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, and a load lock chamber integrated with a cooling function.
In some optional embodiments, after the step S5 of cooling the wafer in the cooling chamber, referring to fig. 3, the thin film deposition method further includes:
s6, depositing a fourth metal layer on the wafer deposited with the third metal layer in a fourth deposition chamber by adopting a fourth magnetron sputtering method;
the fourth deposition chamber is a magnetron sputtering chamber for performing deposition of a fourth metal layer in the thin film deposition apparatus, for example, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the fourth deposition chamber, a cooling chamber, and a loading and unloading chamber, the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the fourth deposition chamber, the cooling chamber, and the loading and unloading chamber surround the transfer chamber, and a robot in the transfer chamber can transfer wafers between the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the fourth deposition chamber, the cooling chamber, and the loading and unloading chamber. Alternatively, the thin film deposition apparatus includes, but is not limited to, a transfer chamber, the above-described pre-cleaning chamber, a first deposition chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a load lock chamber integrated with a cooling function. The fourth deposition chamber has substantially the same structure as the second and third deposition chambers, and the target material is different, that is, the target material in the fourth deposition chamber is the same as the fourth metal layer. The fourth magnetron sputtering method is the same as the second and third magnetron sputtering methods, and is used for forming a fourth metal layer. In addition, the base in the fourth deposition chamber is integrated with a cooling device for cooling the wafer.
And cooling the wafer by controlling the temperature of the base adopted by the fourth magnetron sputtering method, and controlling the temperature of the fourth wafer after the deposition of the fourth metal layer is finished so as to promote the mutual solubility of the first metal layer and the wafer. That is, by controlling the wafer temperature to the fourth wafer temperature, it is beneficial to further increase the generation of the miscible microstructure. Optionally, the temperature of the fourth wafer is greater than or equal to 300 ℃ and less than or equal to 330 ℃. Optionally, the temperature of the susceptor is lower than 0 ℃ to cool the wafer. When the fourth metal layer is deposited by the fourth magnetron sputtering method, the wafer temperature may be increased due to the high energy of particles and the long deposition time compared to the time for depositing the first metal layer by the first magnetron sputtering method in the magnetron sputtering process, and in this case, the wafer needs to be cooled by the base to control the wafer temperature at the fourth wafer temperature.
As can be seen from the above, in the steps S1 to S6, after the deposition of all the metal layers is completed, the wafer temperature is always controlled within the temperature range capable of promoting the mutual solubility of the first metal layer and the wafer, that is, by controlling the temperature of the wafer in the whole deposition process and keeping the wafer temperature between 210 ℃ and 350 ℃, the mutual solubility effect of the first metal layer and the wafer can be improved, and a more ideal mutual solubility structure can be obtained, so that the chip contact resistance can be reduced, and the product performance can be improved.
In one embodiment, the wafer is a silicon wafer; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel vanadium; the fourth metal layer is silver. The thin film deposition method provided by the embodiment of the invention comprises the steps S1 to S6. In this case, in the step S2, the susceptor temperature is 300 ℃ or higher and 380 ℃ or lower; the pressure of the chamber is more than or equal to 2mT and less than or equal to 3mT; the thickness of the first metal layer is greater than or equal to
And is less than or equal to +>
The temperature of the wafer after the process is finished is more than or equal to 300 ℃ and less than or equal to 320 ℃.
After the step S2 is completed, the step S3 may be directly performed without an annealing process in the prior art, so that a wafer does not need to be transferred between the thin film deposition apparatus and the annealing apparatus, thereby not only simplifying the process steps and improving the productivity, but also preventing the first metal layer from being exposed in the atmospheric environment, thereby ensuring the bonding force between metals and improving the product performance.
In the step S3, the temperature of the base is lower than 0 ℃, for example, 20 ℃ below zero; the process gas comprises argon; the pressure of the chamber is more than or equal to 2mT and less than or equal to 3mT; the thickness of the second metal layer is
The temperature of the first wafer after the process is finished is more than or equal to 250 ℃ and less than or equal to 300 ℃.
In step S4, the temperature of the base is lower than 0 ℃, for example, 30 ℃ below zero; the process gas comprises argon and nitrogen; the pressure of the chamber is more than or equal to 2mT and less than or equal to 3mT; the thickness of the third metal layer is greater than or equal to
And is not more than
The temperature of the second wafer after the process is finished is more than or equal to 300 ℃ and less than or equal to 330 ℃.
In the step S5, the wafer is cooled in the cooling chamber, that is, the cooling chamber is added to the thin film deposition apparatus or the loading and unloading chamber integrated with the cooling function is used to cool the wafer, so that the cooling capability can be enhanced and the cooling efficiency can be improved.
In step S5, the method for cooling the wafer in the cooling chamber includes: directly transferring the wafer into a cooling chamber after the nickel-vanadium deposition process is finished, introducing a certain amount of argon, and standing the wafer for 30-60 s under the condition that the pressure of the chamber is kept at 0.5T, so that the wafer is cooled, wherein the temperature of the third wafer after the process is finished is more than or equal to 210 ℃ and less than or equal to 240 ℃.
In the step S6, the temperature of the base is lower than 0 ℃, for example, 20 ℃ below zero; the process gas comprises argon; the pressure of the chamber is more than or equal to 2mT and less than or equal to 3mT; the thickness of the fourth metal layer is greater than or equal to
And is less than or equal to>
The temperature of the fourth wafer after the process is finished is more than or equal to 300 ℃ and less than or equal to 330 ℃.
Fig. 4 is a scanning electron microscope image of the interface between the silicon wafer and the aluminum metal obtained after the completion of the above steps S1 to S6. As shown in fig. 3, the thin film deposition method provided in the embodiment of the present invention can obtain an ideal mutual-soluble structure (i.e., an aluminum-silicon mutual-soluble structure), so that the contact resistance of the chip can be reduced, and the product performance can be effectively improved.
As another technical solution, an embodiment of the present invention further provides a thin film deposition apparatus, which is applied to the thin film deposition method provided in the embodiment of the present invention, and the thin film deposition apparatus includes a pre-cleaning chamber and a first deposition chamber, where the pre-cleaning chamber is configured to perform the step S1, that is, to remove an oxide layer on a surface of a wafer to be deposited by performing a reduction reaction with the oxide layer.
Referring to fig. 5, a susceptor 2 and a deposition ring 3 surrounding the susceptor 2 are disposed in a first deposition chamber 1, wherein the susceptor 2 has a heating function, i.e., a heating device is integrated therein for heating a wafer. The deposition ring 3 has an annular support portion 31, and the top end of the annular support portion 31 is higher than the upper surface of the susceptor 2 for supporting the lower surface edge region of the wafer 5. For the back side metallization process, the surface to be deposited of the wafer 5 is the back side of the wafer, i.e. the front side of the wafer is opposite to the surface of the pedestal for bearing the wafer, in this case, in order to avoid the damage of the front side of the wafer due to the contact with the pedestal, the edge area of the lower surface of the wafer 5 is supported by the top end of the annular support portion 31, so that a gap can be formed between the front side of the wafer and the surface of the pedestal to protect the front side pattern of the wafer. Optionally, the gap is greater than or equal to 2mm.
However, in the continuous mass production process, as the energy of the high-energy target material atoms is continuously enriched in the lower groove of the deposition ring and the temperature rises, the temperature of the deposition ring 3 close to the annular support portion 31 is abnormally high, so that an obvious temperature difference exists between the edge and the center of the wafer, and further the wafer 5 generates a larger warpage after the magnetron sputtering process, and the larger warpage of the wafer surface brings a higher risk of fragments. In order to solve this problem, a cooling channel 32 for conveying a cooling medium (e.g., cooling water) is optionally provided in the deposition ring 3, and an inlet and an outlet of the cooling channel 32 are connected to a cooling circulation system (not shown) through two flexible pipes 4, respectively. Because the base 2 is generally liftable, the arrangement of the two flexible pipelines 4 can ensure that the lifting motion of the base 2 is normally carried out. When the magnetron sputtering process is carried out, the cooling medium is circularly introduced into the cooling channel 32, so that the surface temperature of the deposition ring 3 can be ensured to be stabilized at a lower level, and the problem of wafer warping caused by the accumulated temperature of the deposition ring 3 is solved.
In one embodiment, wafer 5 is a silicon wafer; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel vanadium; the fourth metal layer is silver. The semiconductor processing equipment provided by the embodiment of the invention is applied to the film deposition method comprising the steps S1 to S6. In this case, the semiconductor processing equipment further comprises a transfer chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber and a load-unload chamber, wherein the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the fourth deposition chamber, the cooling chamber and the load-unload chamber are surrounded around the transfer chamber, and a robot in the transfer chamber can transfer wafers among the pre-cleaning chamber, the first deposition chamber, the second deposition chamber, the third deposition chamber, the fourth deposition chamber, the cooling chamber and the load-unload chamber. The first to fourth deposition chambers described above are used to achieve deposition of an aluminum/titanium/nickel vanadium/silver stack on the back side of a silicon wafer. Or the device also comprises a transfer chamber, a second deposition chamber, a third deposition chamber, a fourth deposition chamber and a loading and unloading chamber integrated with a cooling function.
Alternatively, the structures of the second deposition chamber, the third deposition chamber, and the fourth deposition chamber may be substantially the same as the structure of the first deposition chamber shown in fig. 5, and the material of the target and the structure and function of the pedestal are different, specifically, the material of the target in each deposition chamber is the same as the material of the metal layer to be deposited, and the pedestals in the second deposition chamber, the third deposition chamber, and the fourth deposition chamber have a cooling function, i.e., are integrated with a cooling device, for cooling the wafer, and the pedestal in the first deposition chamber has a heating function, i.e., is integrated with a heating device, for heating the wafer.
In summary, in the technical scheme of the thin film deposition method and the thin film deposition apparatus provided in the embodiments of the present invention, a reduction precleaning technique is adopted, that is, a reduction gas is introduced into a precleaning chamber to perform a reduction reaction with an oxide layer on a surface to be deposited of a wafer to remove the oxide layer on the surface to be deposited of the wafer, so that the oxide layer can be removed to the lowest extent of damage, and atoms on the surface of the silicon wafer are prevented from being activated, thereby preventing an abnormal silicon bump failure morphology from occurring; and when the first metal layer which can be mutually dissolved with the wafer is deposited on the surface to be deposited of the wafer by adopting the first magnetron sputtering method, the mutual dissolving structure of the first metal layer and the wafer can be obtained by controlling the temperature of the base, so that the annealing process in the prior art can be omitted, the wafer does not need to be transmitted between the magnetron sputtering equipment and the annealing equipment, the process steps can be simplified, the productivity is improved, the first metal layer can be prevented from being exposed in the atmospheric environment, the bonding force between metals can be ensured, and the product performance can be improved.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (11)
1. A thin film deposition method, comprising:
introducing reducing gas into the pre-cleaning chamber to perform reduction reaction with the oxide layer on the surface to be deposited of the wafer to remove the oxide layer;
depositing a first metal layer which can be mutually dissolved with the wafer on the surface to be deposited of the wafer by adopting a first magnetron sputtering method in a first deposition chamber;
and obtaining a mutual soluble structure of the first metal layer and the wafer by controlling the temperature of a base adopted by the first magnetron sputtering method.
2. The thin film deposition method according to claim 1, wherein the temperature of the susceptor in the first magnetron sputtering method is controlled to 300 ℃ or higher and 380 ℃ or lower.
3. The method of claim 1, wherein after depositing a first metal layer that is miscible with the wafer on the surface to be deposited of the wafer in the first deposition chamber using a first magnetron sputtering method, the method further comprises:
depositing a second metal layer on the wafer deposited with the first metal layer in a second deposition chamber by adopting a second magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the second magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the second metal layer at the first wafer so as to promote the mutual solubility of the first metal layer and the wafer.
4. The thin film deposition method of claim 3, wherein after depositing a second metal layer on the wafer on which the first metal layer is deposited using a second magnetron sputtering method in a second deposition chamber, the thin film deposition method further comprises:
depositing a third metal layer on the wafer deposited with the second metal layer in a third deposition chamber by adopting a third magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the third magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the third metal layer at the second wafer so as to promote the mutual solubility of the first metal layer and the wafer.
5. The thin film deposition method of claim 4, wherein after depositing a third metal layer on the wafer on which the second metal layer is deposited using a third magnetron sputtering method in a third deposition chamber, the thin film deposition method further comprises:
and cooling the wafer in a cooling chamber, and controlling the temperature of the wafer at a third wafer temperature so as to promote mutual solubility of the first metal layer and the wafer.
6. The thin film deposition method of claim 5, further comprising, after the cooling the wafer in the cooling chamber:
depositing a fourth metal layer on the wafer deposited with the third metal layer in a fourth deposition chamber by adopting a fourth magnetron sputtering method;
and cooling the wafer by controlling the temperature of the base adopted by the fourth magnetron sputtering method, and controlling the temperature of the wafer after the deposition of the fourth metal layer is finished at the fourth wafer so as to promote the mutual solubility of the first metal layer and the wafer.
7. The thin film deposition method of claim 6, wherein the first wafer temperature is greater than or equal to 250 ℃ and less than or equal to 300 ℃; the temperature of the second wafer is more than or equal to 300 ℃ and less than or equal to 330 ℃; the temperature of the third wafer is more than or equal to 210 ℃ and less than or equal to 240 ℃; the temperature of the fourth wafer is more than or equal to 300 ℃ and less than or equal to 330 ℃.
8. The thin film deposition method according to claim 6, wherein the temperature of the susceptor in the second magnetron sputtering method is controlled to be lower than 0 ℃; controlling the temperature of the base in the third magnetron sputtering method to be lower than 0 ℃; and controlling the temperature of the base in the fourth magnetron sputtering method to be lower than 0 ℃.
9. The method of claim 6, wherein the wafer is made of silicon; the first metal layer is aluminum; the second metal layer is titanium; the third metal layer is nickel vanadium; the fourth metal layer is silver.
10. A thin film deposition apparatus applied to the thin film deposition method according to any one of claims 1 to 9, the thin film deposition apparatus comprising the pre-cleaning chamber and the first deposition chamber, wherein the first deposition chamber is provided therein with a susceptor and a deposition ring disposed around the susceptor, the deposition ring having an annular support portion whose top end is higher than an upper surface of the susceptor for supporting a lower surface edge region of the wafer; the base in the first deposition chamber has a heating function;
and a cooling channel for conveying a cooling medium is arranged in the deposition ring, and an inlet and an outlet of the cooling channel are respectively connected with a cooling circulation system through two flexible pipelines.
11. The thin film deposition apparatus according to claim 10, further comprising a second deposition chamber, a third deposition chamber, a fourth deposition chamber, a cooling chamber, and a loading/unloading chamber, or further comprising a second deposition chamber, a third deposition chamber, a fourth deposition chamber, and a loading/unloading chamber having a cooling function; wherein the susceptors in the second deposition chamber, the third deposition chamber and the fourth deposition chamber have a cooling function.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117116786A (en) * | 2023-10-20 | 2023-11-24 | 粤芯半导体技术股份有限公司 | Preparation method of back metallization of IGBT (insulated Gate Bipolar transistor) wafer |
| CN117198915A (en) * | 2023-11-07 | 2023-12-08 | 粤芯半导体技术股份有限公司 | Method for monitoring wafer back surface process and method for preparing monitoring wafer |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117116786A (en) * | 2023-10-20 | 2023-11-24 | 粤芯半导体技术股份有限公司 | Preparation method of back metallization of IGBT (insulated Gate Bipolar transistor) wafer |
| CN117116786B (en) * | 2023-10-20 | 2024-03-01 | 粤芯半导体技术股份有限公司 | Preparation method of back metallization of IGBT (insulated Gate Bipolar transistor) wafer |
| CN117198915A (en) * | 2023-11-07 | 2023-12-08 | 粤芯半导体技术股份有限公司 | Method for monitoring wafer back surface process and method for preparing monitoring wafer |
| CN117198915B (en) * | 2023-11-07 | 2024-02-27 | 粤芯半导体技术股份有限公司 | Method for monitoring wafer back surface process and method for preparing monitoring wafer |
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