Annealing method of bonded wafer
By cleaning the oxide layer decomposing residues when the heating of the furnace tube equipment is raised, the problem of oxide layer residue contamination during the SOI wafer annealing process is solved, and the surface of the bonded wafer is cleaned and planarized.
Patent Information
- Application Number
- CN202510610262.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2025-08-12
AI Technical Summary
During the annealing process of the SOI wafer, the oxide layer decomposes residues to contaminate the furnace tube equipment and attaches to the wafer surface, resulting in particle aggregation problems.
The residue is cleaned by passing hydrogen into the furnace tube equipment when the temperature is raised, and discharged before the annealing process to prevent the residue from adhering to the bonded wafer surface.
It effectively improves the particle aggregation problem on the bonded wafer surface and improves the flatness and cleanliness of the wafer surface.
Smart Images
Figure CN120473390A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of integrated circuits, and in particular to an annealing method for a bonded wafer. Background Art
[0002] In the preparation process of SOI (Silicon-On-Insulator) wafers, after the bonding of the supporting substrate and the device substrate in the SOI wafer is completed, that is, after the bonded wafer is formed, the SOI wafer usually needs to be annealed to flatten the surface of the SOI wafer. Currently, the annealing of SOI wafers needs to be carried out by furnace tube equipment. Since the surface of the SOI wafer usually has an oxide layer, when high-temperature annealing is performed, the oxide layer on the surface of the SOI wafer will decompose and form decomposition residues inside the furnace tube equipment, thereby polluting the internal environment of the furnace tube equipment. In addition, the oxide layer decomposition residues are easily moved with the airflow and attached to the surface of the SOI wafer that is subsequently annealed, thereby causing the problem of particle aggregation on the surface of the SOI wafer. Summary of the Invention
[0003] The object of the present invention is to provide an annealing method for a bonded wafer, so as to improve the problem of particle aggregation on the surface of the bonded wafer.
[0004] To achieve the above object, the present invention provides a method for annealing a bonded wafer, comprising:
[0005] Provide furnace tube equipment;
[0006] performing a temperature increase process to increase the temperature of the furnace tube device from a first temperature to a target temperature at a set temperature increase rate, introducing hydrogen into the furnace tube device when the temperature reaches the target temperature, and discharging the hydrogen in the furnace tube device after maintaining the temperature for a preset time;
[0007] performing a cooling process to cool the furnace tube device from the target temperature to the first temperature at a set cooling rate;
[0008] Providing a bonding wafer, wherein an oxide layer is formed on one surface of the bonding wafer;
[0009] The bonded wafer is placed in the furnace tube equipment to perform an annealing process.
[0010] Optionally, in the annealing method for the bonded wafer, when performing the temperature increase process, the method further includes:
[0011] performing a first temperature rising process, heating the furnace tube device from the first temperature to a second temperature at a first heating rate, and continuously introducing argon gas into the furnace tube device during the heating process;
[0012] Perform a second heating process to heat the furnace tube device from the second temperature to the target temperature at a second heating rate, and continuously introduce argon into the furnace tube device during the heating process, and stop introducing the argon and exhaust the argon in the furnace tube device when the temperature reaches the target temperature.
[0013] Optionally, in the bonded wafer annealing method, the first temperature is 400°C to 600°C.
[0014] Optionally, in the bonded wafer annealing method, the second temperature is 700°C to 800°C.
[0015] Optionally, in the bonded wafer annealing method, the first heating rate is 4°C / min to 6°C / min.
[0016] Optionally, in the bonded wafer annealing method, the second heating rate is 1°C / min to 3°C / min.
[0017] Optionally, in the annealing method for the bonded wafer, when performing the temperature reduction process, the method further includes:
[0018] During the process of cooling the furnace tube device from the target temperature to the first temperature at a set cooling rate, argon gas is introduced into the furnace tube device, and when the temperature is cooled to the first temperature, the argon gas in the furnace tube device is discharged.
[0019] Optionally, in the bonded wafer annealing method, when performing the annealing process, the method further includes:
[0020] A mixed gas of argon and hydrogen is introduced into the furnace tube equipment, and the flow rates of the hydrogen and argon are both 10 slm to 20 slm.
[0021] Optionally, in the annealing method for the bonded wafer, the set cooling rate is 4°C / min to 6°C / min.
[0022] Optionally, in the annealing method for the bonded wafer, when the hydrogen gas is introduced into the furnace tube equipment, the gas flow rate of the hydrogen gas is 20 slm to 30 slm, and the preset time is 60 min to 70 min.
[0023] In the annealing method for bonded wafers provided by the present invention, a heating process is first performed to heat a furnace tube device from a first temperature to a target temperature at a set heating rate, and hydrogen is introduced into the furnace tube device when the temperature reaches the target temperature, and the hydrogen in the furnace tube device is discharged after the temperature is maintained for a preset time; then, a cooling process is performed to cool the furnace tube device from the target temperature to the first temperature at a set cooling rate; then, a bonded wafer is provided, and an oxide layer is formed on one surface of the bonded wafer; thereafter, the bonded wafer is placed in the furnace tube device to perform an annealing process. In this way, by performing the heating process and introducing hydrogen into the furnace tube device, the oxide layer decomposition residue in the furnace tube device can be cleaned, thereby removing the oxide layer decomposition residue in the furnace tube device. When the bonded wafer is subsequently annealed using the furnace tube device, the oxide layer decomposition residue remaining in the furnace tube device can be prevented from adhering to the surface of the bonded wafer, thereby improving the problem of particle aggregation on the surface of the bonded wafer. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 1 is a schematic flow chart of a method for annealing a bonded wafer according to an embodiment of the present invention;
[0025] Figure 2 is a schematic diagram of a structure formed in the annealing method of a bonded wafer according to an embodiment of the present invention;
[0026] Figure 3 1 is a temperature diagram of a temperature increase process, a temperature decrease process and an annealing process in an annealing method for a bonded wafer according to an embodiment of the present invention;
[0027] Figures 4 to 13 1 is a schematic diagram of the surface roughness of a bonded wafer in the annealing method of a bonded wafer according to an embodiment of the present invention;
[0028] The description of the accompanying drawings is as follows:
[0029] 100 - bonding wafer; 101 - support wafer; 102 - device wafer; 103 - insulating layer; 110 - oxide layer. DETAILED DESCRIPTION
[0030] The following is a further detailed description of the bonded wafer annealing method proposed by the present invention, in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.
[0031] Figure 1 FIG. 1 is a flow chart of the annealing method for bonded wafers provided by an embodiment of the present invention. Figure 1 As shown, the annealing method of the bonded wafer provided in this embodiment includes:
[0032] Step S1: providing furnace tube equipment;
[0033] Step S2: performing a temperature increase process to increase the temperature of the furnace tube device from a first temperature to a target temperature at a set temperature increase rate, introducing hydrogen into the furnace tube device when the temperature reaches the target temperature, and maintaining the temperature for a preset time before discharging the hydrogen in the furnace tube device;
[0034] Step S3: performing a cooling process to cool the furnace tube device from the target temperature to the first temperature at a set cooling rate;
[0035] Step S4: providing a bonding wafer, wherein an oxide layer is formed on one surface of the bonding wafer;
[0036] Step S5: placing the bonded wafer in the furnace tube equipment to perform an annealing process.
[0037] Figure 2 is a schematic diagram of a structure formed in the annealing method of a bonded wafer according to an embodiment of the present invention; Figure 3 Figure 3 1 is a temperature diagram of a temperature increase process, a temperature decrease process and an annealing process in an annealing method for a bonded wafer according to an embodiment of the present invention; Figures 4 to 13 Schematic diagram of the surface roughness of the bonded wafer in the annealing method of the bonded wafer according to the embodiment of the present invention; Figures 2 to 13 The annealing method for the bonded wafer provided in this embodiment is described in more detail.
[0038] First, step S1 is performed to provide a furnace tube device. Exemplarily, the furnace tube device can be a vertical furnace tube.
[0039] Next, step S2 is executed to perform a temperature rise treatment to heat the furnace tube device from the first temperature to the target temperature at a set temperature rise rate, and hydrogen is introduced into the furnace tube device when the temperature is raised to the target temperature, and the hydrogen in the furnace tube device is discharged after being kept for a preset time, that is, the temperature rise treatment is performed before the bonded wafer 100 is loaded into the furnace tube device.
[0040] Specifically, the method for performing the temperature rising treatment includes: first, performing a first temperature rising treatment, heating the furnace tube device from the first temperature to the second temperature at a first temperature rising rate, and continuously introducing argon (Ar) into the furnace tube device during the temperature rising process.
[0041] Optionally, the first temperature is 400° C. to 600° C., such as 450° C., 500° C., or 550° C.; the second temperature is 700° C. to 800° C., such as 750° C., 760° C., or 780° C. The first heating rate is 4° C. / min to 6° C. / min.
[0042] In this embodiment, during the first temperature rising treatment process, the gas flow rate of argon (Ar) is 20slm~30slm, that is, during the first temperature rising treatment process, the gas in the furnace tube equipment is pure argon to ensure that the oxygen content in the gas in the furnace tube equipment is less than 10ppm, thereby avoiding trace impurity gases from causing adverse effects on the bonded wafer 100 in the subsequent annealing process.
[0043] Next, a second heating process is performed, heating the furnace tube device from the second temperature to the target temperature at a second heating rate. Argon gas is continuously introduced into the furnace tube device during the heating process, and the introduction of argon gas is stopped and the argon gas in the furnace tube device is exhausted when the temperature reaches the target temperature. During the second heating process, the second heating rate can be lower than the first heating rate to ensure uniform temperature distribution within the furnace tube device and reduce temperature fluctuations caused by air flow or local airflow disturbances. The second heating rate can be 1°C / min to 3°C / min.
[0044] In this embodiment, while heating the furnace tube device from the second temperature to the target temperature, argon gas continues to be introduced into the furnace tube device. The gas flow rate of the argon gas can be 20lm to 30slm. After reaching the target temperature, the introduction of argon gas is stopped and the argon gas in the furnace tube device is discharged.
[0045] Furthermore, when the temperature in the furnace tube device rises to the target temperature, the argon gas in the furnace tube device is exhausted, and hydrogen gas is then introduced into the furnace tube device and maintained for a preset time. That is, after hydrogen gas is introduced into the furnace tube device, the target temperature is maintained at a constant temperature for a preset time. In this way, the decomposition residues of the oxide layer (such as the silicon dioxide layer) in the furnace tube device can be cleaned, thereby removing the decomposition residues of the oxide layer in the furnace tube device. When the bonded wafer 100 is subsequently annealed using the furnace tube device, the decomposition residues of the oxide layer remaining in the furnace tube device can be prevented from adhering to the surface of the bonded wafer 100, thereby improving the problem of particle aggregation on the surface of the bonded wafer 100.
[0046] Exemplarily, the target temperature of the furnace tube equipment is 1000°C to 1200°C, such as 1050°C, 1100°C or 1150°C.
[0047] In this embodiment, when the temperature in the furnace tube equipment is heated to 1000°C to 1200°C, hydrogen is introduced into the furnace tube equipment with a gas flow rate of 20slm to 30slm, and the temperature is maintained at 1000°C to 1200°C for a preset time, which can be 60min to 70min, preferably 60min, to ensure that the hydrogen content in the furnace tube equipment can clean the oxide layer decomposition residues in the furnace tube equipment.
[0048] Afterwards, the hydrogen in the furnace tube device is discharged. When the hydrogen in the furnace tube device is discharged, the oxide layer decomposition residue in the furnace tube device can be discharged together, thereby reducing the problem of contamination or particle aggregation caused by the residue in the furnace tube device to the subsequent bonded wafer 100.
[0049] Next, step S3 is executed to perform a cooling process to cool the furnace tube equipment from the target temperature to the first temperature at a set cooling rate, that is, to cool the furnace tube equipment to 400° C. to 600° C.
[0050] In addition, during the cooling process, argon gas is introduced into the furnace tube equipment while cooling the furnace tube equipment from the target temperature to the first temperature at a set cooling rate. In this way, the oxygen content in the furnace tube equipment can be reduced, thereby preparing for the subsequent annealing process.
[0051] Optionally, when performing the cooling treatment, the cooling rate is set to 4°C / min to 6°C / min to reduce the temperature inside the furnace tube equipment to the temperature requirement of the subsequent annealing process, in preparation for the subsequent annealing process.
[0052] Afterwards, when the temperature is lowered to the first temperature, the argon gas in the furnace tube equipment is discharged, that is, before the bonded wafer is placed in the furnace tube equipment, the argon gas in the furnace tube equipment is discharged. In this way, the oxide layer decomposition residues remaining in the furnace tube equipment can be further discharged, etc., to avoid contamination or particle aggregation problems on the bonded wafers subsequently loaded into the furnace tube equipment.
[0053] Then, if Figure 2 As shown, step S4 is performed to provide a bonded wafer 100, wherein an oxide layer 110 is formed on the surface of the bonded wafer 100. Specifically, the oxide layer 110 can be a silicon oxide layer. The bonded wafer 100 is a bonded wafer.
[0054] Specifically, the bonding wafer 100 includes a supporting wafer 101 and a device wafer 102, wherein the supporting wafer 101 has a first surface and a second surface arranged opposite to each other, the device wafer 102 is bonded to the first surface of the supporting wafer 101, an insulating layer 103 is formed between the device wafer 102 and the supporting wafer 101, and an oxide layer 110 is formed on the second surface of the supporting wafer 101.
[0055] Next, step S5 is performed to place the bonded wafer 100 in the furnace tube device to perform an annealing process, that is, the bonded wafer 100 is loaded into the furnace tube device and an annealing process is performed to reduce the surface roughness of the bonded wafer 100. Since, in the aforementioned steps, the oxide layer decomposition residues in the furnace tube device are cleaned by performing the temperature increase process and using hydrogen gas, thereby removing the oxide layer decomposition residues in the furnace tube device, when the bonded wafer 100 is subjected to the annealing process using the furnace tube device, the oxide layer decomposition residues remaining in the furnace tube device can be prevented from adhering to the surface of the bonded wafer 100, thereby improving the problem of particle aggregation on the surface of the bonded wafer 100.
[0056] Specifically, during the annealing process, argon and hydrogen are re-introduced into the furnace tube device. The argon gas flow rate can be 10slm to 20slm; the hydrogen gas flow rate can be 10slm to 20slm. During the annealing process, the temperature of the furnace tube device is raised to a target temperature of 1000°C to 1200°C and maintained at that temperature for 1 to 3 hours to achieve high-temperature annealing of the bonded wafer 100.
[0057] During the annealing process, high temperature can accelerate the migration rate of material molecules on the surface of the bonded wafer 100, so that some uneven parts of the surface of the bonded wafer 100, such as protrusions or depressions, gradually become flat due to the migration of atoms under high temperature, that is, the surface of the bonded wafer is flattened.
[0058] Illustratively, during the annealing process, the temperature inside the furnace tube device can be raised to the target temperature by gradually increasing the temperature. For example, the temperature inside the furnace tube device is first raised to 700°C to 800°C and maintained for 10s to 25s; then, the temperature inside the furnace tube device is raised to 1000°C to 1200°C and maintained at a constant temperature for 1 hour to 3 hours, for example, 2 hours. In this way, the bonded wafer 100 can be evenly heated during the temperature increase process, avoiding thermal stress concentration caused by local excessively high or low temperatures.
[0059] Figure 3 A temperature diagram of sequentially performing temperature increase, temperature decrease, and annealing processes provided in an embodiment of the present invention. Figure 3The horizontal axis represents time, and the vertical axis represents temperature. S1 represents the first temperature stage, during which the argon gas flow rate within the furnace tube equipment is A1, for example, 20slm to 30slm; S2 represents the second temperature stage, during which the argon gas flow rate within the furnace tube equipment is A2, for example, 20slm to 30slm; S3 represents the target temperature stage, during which the hydrogen gas flow rate within the furnace tube equipment is A3, for example, 20slm to 30slm; S4 represents the cooling process to the first temperature stage, during which the argon gas flow rate within the furnace tube equipment is A4, for example, 20slm to 30slm. The temperature of T1 is 500°C, the temperature of T2 is 700°C to 800°C, and the temperature of T3 is 1000°C to 1200°C.
[0060] The following is a further explanation of the annealing method of the bonded wafer 100 provided in this embodiment in combination with five embodiments.
[0061] Table 1 Relationship between target temperature and particle abnormality
[0062]
[0063] In Example 1, the target temperature of the heating treatment is 1000° C. to 1200° C. When the furnace tube device is heated to 1000° C. to 1200° C., hydrogen is introduced into the furnace tube device for 0.5 hours (h). After the annealing process is performed, the surface of the bonded wafer 100 is subjected to roughness and particle detection, as shown in FIG. Figure 4 and Figure 5 As shown, the surface roughness of the bonded wafer 100 is 0.17 nm, and there are some abnormal particles on the surface of the bonded wafer 100. By analyzing the components of the abnormal defects, it is determined that the components of the abnormal defects are Si (silicon) and O (oxygen), that is, silicon dioxide decomposition products.
[0064] In the second embodiment, the target temperature of the heating treatment is 900°C to 1000°C. When the furnace tube device is heated to 900°C to 1000°C, hydrogen is introduced into the furnace tube device for 1 hour. After the annealing process is performed, the surface roughness and particle detection of the bonded wafer 100 are performed. Figure 6 and Figure 7 As shown, the surface roughness of the bonded wafer 100 is 0.18 nm, and there are abnormal particles on the surface of the bonded wafer 100.
[0065] In Example 3, the target temperature of the heating treatment is 900°C to 1000°C. When the furnace tube device is heated to 900°C to 1000°C, hydrogen is introduced into the furnace tube device for 2 hours. After the annealing process, the surface roughness and particle detection of the bonded wafer 100 are performed. Figure 8 and Figure 9 As shown, the surface roughness of the bonded wafer 100 is 0.17 nm, and there are abnormal particles on the surface of the bonded wafer 100.
[0066] In the fourth embodiment, the target temperature of the heating treatment is 1000°C to 1200°C. When the furnace tube device is heated to 1000°C to 1200°C, hydrogen is introduced into the furnace tube device for 1 hour. After the annealing process is performed, the surface roughness and particle detection of the bonded wafer 100 are performed. Figure 10 and Figure 11 As shown, the surface roughness of the bonded wafer 100 is 0.17 nm, and there is no abnormality in the particles on the surface of the bonded wafer 100.
[0067] In Example 5, the target temperature of the heating treatment is 1000°C to 1200°C. When the furnace tube device is heated to 1000°C to 1200°C, argon gas is introduced into the furnace tube device for 1 hour. After the annealing process is performed, the surface roughness and particle detection of the bonded wafer 100 are performed. Figure 12 and Figure 13 As shown, the surface roughness of the bonded wafer 100 is 0.18 nm, and there are abnormal particles on the surface of the bonded wafer 100.
[0068] By comparing the above five embodiments, it can be seen that the annealing method for bonded wafers provided by the present embodiment, i.e., embodiment four, has a target temperature of 1000°C to 1200°C, and hydrogen is introduced into the furnace tube equipment when the furnace tube equipment is heated to 1000°C to 1200°C, and the hydrogen introduction time is 1 hour. Compared with the other four embodiments, the annealing method for bonded wafers provided by the present embodiment can effectively avoid the problem of abnormal particles on the surface of the bonded wafer, and the annealing method for bonded wafers provided by the present embodiment, after executing the annealing process, the roughness of the surface of the bonded wafer is 0.17, which is less than the roughness of embodiments two and five. Therefore, the annealing method for bonded wafers provided by the present embodiment can avoid the problem of abnormal particles on the surface of the bonded wafer while reducing the roughness of the surface of the bonded wafer.
[0069] In addition, the annealing method for bonded wafers provided in this embodiment can avoid the problem of abnormal particles on the surface of the bonded wafers without changing the hardware structure of the furnace equipment.
[0070] In summary, in the annealing method for a bonded wafer provided in an embodiment of the present invention, a heating process is first performed to heat the furnace tube device from a first temperature to a target temperature at a set heating rate, and hydrogen is introduced into the furnace tube device when the temperature is raised to the target temperature, and the hydrogen in the furnace tube device is discharged after the temperature is maintained for a preset time; then, a cooling process is performed to cool the furnace tube device from the target temperature to a first temperature at a set cooling rate, and the hydrogen in the furnace tube device is discharged; then, a bonded wafer is provided, and an oxide layer is formed on one surface of the bonded wafer; thereafter, the bonded wafer is placed in the furnace tube device to perform an annealing process. In this way, by performing the heating process and by introducing hydrogen into the furnace tube device, the oxide layer decomposition residue in the furnace tube device can be cleaned, thereby removing the oxide layer decomposition residue in the furnace tube device. When the furnace tube device is subsequently used to perform an annealing process on the bonded wafer, the oxide layer decomposition residue remaining in the furnace tube device can be prevented from adhering to the surface of the bonded wafer, thereby improving the problem of particle aggregation on the surface of the bonded wafer.
[0071] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.
[0072] Furthermore, it should be recognized that although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent variations, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.
Claims
1. A method for annealing a bonded wafer, characterized in that: include: Provide furnace tube equipment; performing a temperature increase process to increase the temperature of the furnace tube device from a first temperature to a target temperature at a set temperature increase rate, introducing hydrogen into the furnace tube device when the temperature reaches the target temperature, and discharging the hydrogen in the furnace tube device after maintaining the temperature for a preset time; performing a cooling process to cool the furnace tube device from the target temperature to the first temperature at a set cooling rate; Providing a bonding wafer, wherein an oxide layer is formed on one surface of the bonding wafer; The bonded wafer is placed in the furnace tube equipment to perform an annealing process.
2. The annealing method for a bonded wafer according to claim 1, wherein: When performing the temperature raising process, the method further includes: performing a first temperature rising process to raise the temperature of the furnace tube device from the first temperature to a second temperature at a first temperature rising rate, and continuously introducing argon gas into the furnace tube device during the temperature rising process; Perform a second heating process to heat the furnace tube device from the second temperature to the target temperature at a second heating rate, and continuously introduce argon into the furnace tube device during the heating process, and stop introducing the argon and exhaust the argon in the furnace tube device when the temperature reaches the target temperature.
3. The annealing method for a bonded wafer according to claim 2, wherein: The first temperature is 400°C to 600°C.
4. The annealing method for a bonded wafer according to claim 2, wherein: The second temperature is 700°C to 800°C.
5. The annealing method for a bonded wafer according to claim 2, wherein: The first heating rate is 4°C / min to 6°C / min.
6. The annealing method for a bonded wafer according to claim 2, wherein: The second heating rate is 1°C / min to 3°C / min.
7. The annealing method for a bonded wafer according to claim 1, wherein: When performing the cooling process, the method further includes: During the process of cooling the furnace tube device from the target temperature to the first temperature at a set cooling rate, argon gas is introduced into the furnace tube device, and when the temperature is cooled to the first temperature, the argon gas in the furnace tube device is discharged.
8. The annealing method for a bonded wafer according to claim 1, wherein: When performing the annealing process, the method further includes: A mixed gas of argon and hydrogen is introduced into the furnace tube equipment, and the flow rates of the hydrogen and argon are both 10 slm to 20 slm.
9. The annealing method for a bonded wafer according to claim 1, wherein: The set cooling rate of the cooling treatment is 4°C / min to 6°C / min.
10. The annealing method for a bonded wafer according to claim 1, wherein: When the hydrogen is introduced into the furnace tube equipment, the gas flow rate of the hydrogen is 20 slm to 30 slm, and the preset time is 60 min to 70 min.