CN109830437B - Wafer heat treatment method and wafer - Google Patents
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- CN109830437B CN109830437B CN201910072442.XA CN201910072442A CN109830437B CN 109830437 B CN109830437 B CN 109830437B CN 201910072442 A CN201910072442 A CN 201910072442A CN 109830437 B CN109830437 B CN 109830437B
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Abstract
The invention provides a wafer heat treatment method and a wafer, wherein the wafer heat treatment method comprises the following steps: placing the wafer in an inert atmosphere for pre-heat preservation treatment; heating the wafer subjected to the pre-heat preservation treatment to a first temperature at a first heating rate; then placing the wafer in a first oxidizing atmosphere, and heating from the first temperature to a second temperature at a second heating rate, wherein the second heating rate is smaller than the first heating rate; placing the wafer in a second oxidizing atmosphere, and heating from the second temperature to a third temperature at a third heating rate, wherein the second heating rate is smaller than the third heating rate; placing the wafer in an inert atmosphere and carrying out primary heat preservation at a third temperature; and after the primary heat preservation is finished, the temperature is reduced from the third temperature to the fourth temperature at different cooling rates for secondary heat preservation. By the method, the wafer with excellent DZ area and high-density BMD area, long minority carrier lifetime, low content of interstitial iron ions and small slip deviation can be obtained.
Description
Technical Field
The invention relates to the technical field of wafers, in particular to a wafer heat treatment method and a wafer.
Background
With the development success of 16M FLASH and 256M DRAM, which integrate 1000 ten thousand transistors, the era of Ultra-large Scale Integration (ULSI) has entered. The rapid increase in integration of ULSI circuits is largely dependent on two factors: firstly, the perfect crystal growth technology reaches an extremely high level; secondly, the manufacturing equipment is continuously perfect, and the improvement of the processing precision, the automation degree and the reliability enables the size of the device to enter the deep submicron level field. So that larger and more perfect silicon wafers can meet the ultra-small and high density requirements of ULST. It is important to avoid defects in large silicon wafers and provide a wafer with good DZ (dead Zone) area and high-density BMD (Bulk Micro Defect) area.
In the conventional cz (czochralski) czochralski method, different regions may be generated depending on the pulling rate, for example, I (Interstitial-Si) region, V (vacancy) region, dsod (direct Surface Oxide defect) region, COP (crystal oriented) Free region, etc., as shown in fig. 1, fig. 1 shows the relationship between the single crystal growth rate and the crystal defect, wherein a shows I region, b shows V region, c shows COP Free region, different regions are formed at different pulling rates, the pulling rate gradually increases in the direction of the arrow in fig. 1, I region is formed at low pulling rate, V region is formed at high pulling rate, and COP Free region is formed at medium pulling rate. Conventional defects include 1) void type defects: such as FDP (flow Pattern Defect), LSTD (laser Scattering Tomography Defect), COP, etc.; 2) gap type defects: such as LSEPD (Large Secco Etch Pit Defect), LFPD (Large Flow Pattern Defect), etc. Oxygen and other impurities are also easily introduced during the Czochralski process. The oxide precipitates deteriorate the device characteristics in the surface region of the device fabrication; however, the presence of oxygen precipitation can also serve as an IG (Internal Gettering) effective site for Gettering of impurities such as metals, and can correspondingly improve the strength of the device.
Czochralski silicon generally contains metal impurities such as iron, copper, cobalt, nickel and the like, and the existence of the impurities can influence the minority carrier Lifetime (Lifetime) of the monocrystalline silicon, thereby influencing the performance of a device. The methods for reducing metal impurities are generally three: reducing the introduction of heavy metal in polishing, low-temperature annealing and internal gettering. In view of yield and cost, an intrinsic gettering technique is generally selected for removing metal impurities from polished monocrystalline silicon wafers.
In order to obtain a good DZ region and a high density BMD region, many defects and impurities in the silicon wafer need to be eliminated. The conventional method generally selects an annealing treatment or a rapid thermal treatment, but the high temperature treatment causes a slip problem and the like. Although different heat treatment methods are available in the prior art to achieve a certain treatment effect, how to obtain a monocrystalline silicon wafer which can remove metals such as Fe, reduce slippage and has an excellent DZ region and a high-density BMD region in one heat treatment is a problem to be researched.
Disclosure of Invention
Accordingly, the present invention provides a method for heat-treating a wafer, which is used to obtain a wafer with excellent DZ region and high-density BMD region, long minority carrier lifetime, low interstitial iron ion content and small slip deviation.
The invention also provides a wafer.
In order to solve the technical problems, the invention adopts the following technical scheme:
the wafer heat treatment method according to the embodiment of the first aspect of the invention comprises the following steps:
step S1, placing the wafer in an inert atmosphere for pre-heat preservation treatment;
step S2, heating the wafer after the pre-heat preservation treatment to a first temperature at a first heating rate;
step S3, placing the wafer in a first oxidizing atmosphere, and heating from the first temperature to a second temperature at a second heating rate, wherein the second heating rate is smaller than the first heating rate;
step S4, placing the wafer in a second oxidizing atmosphere, and heating from the second temperature to a third temperature at a third heating rate, wherein the second heating rate is smaller than the third heating rate;
step S5, placing the wafer in an inert atmosphere and carrying out primary heat preservation at the third temperature;
and step S6, after the primary heat preservation is finished, the temperature is reduced from the third temperature to the fourth temperature at different temperature reduction rates, and secondary heat preservation is carried out.
Further, the first temperature rise rate is greater than the third temperature rise rate.
Further, in step S3, the first oxidizing atmosphere is oxygen; in step S4, the second oxidizing atmosphere includes oxygen and nitrogen.
Further, in step S6, after the primary heat preservation is finished, the temperature is decreased from the third temperature to a fifth temperature at a first temperature decrease rate, and then decreased from the fifth temperature to the fourth temperature at a second temperature decrease rate.
Further, the first temperature is greater than the fifth temperature.
Further, the first cooling rate is greater than the second cooling rate.
Further, the first temperature reduction rate is 8-12 ℃/min, and the fifth temperature is 650-750 ℃;
the second temperature reduction rate is 1-5 ℃/min, and the fourth temperature is 350-450 ℃.
Further, the fourth temperature is lower than the temperature of the pre-heat preservation treatment.
Further, in step S1, the temperature of the pre-heat-preservation treatment is 450-550 ℃, and the time of the pre-heat-preservation treatment is 20-40 min;
in step S2, the first temperature-increasing rate is 8-12 ℃/min, and the first temperature is 750-850 ℃;
in step S3, the second temperature-increasing rate is 1-3 ℃/min, and the second temperature is 950-1050 ℃;
in step S4, the third temperature-increasing rate is 4-6 ℃/min, and the third temperature is 1150-1250 ℃;
in step S5, the heat preservation time of the primary heat preservation is 30-60 min.
The wafer according to the second aspect of the present invention is obtained by processing the wafer by the above-mentioned wafer heat treatment method.
The technical scheme of the invention at least has one of the following beneficial effects:
according to the wafer heat treatment method, a wafer is placed in an inert atmosphere for pre-heat preservation, the wafer subjected to the pre-heat preservation is quickly heated to a first temperature, then the wafer is placed in a first oxidizing atmosphere and is slowly heated to a second temperature, the wafer is placed in a second oxidizing atmosphere and is quickly heated to a third temperature, the wafer is placed in the inert atmosphere and is subjected to primary heat preservation at the third temperature, and after primary heat preservation is finished, the wafer is cooled to a fourth temperature at different cooling rates for secondary heat preservation. By the method, the wafers in a DZ area and a high-density BMD area can be obtained, the minority carrier lifetime is prolonged, the content of interstitial iron ions is reduced, the pollution caused by devices is effectively prevented, the slippage problem caused by the devices can be controlled, the treatment effect on the wafers is improved, the treatment efficiency is improved, and the treatment cost is reduced.
Drawings
FIG. 1 is a graph showing a relationship between a single crystal growth rate and a crystal defect;
FIG. 2 is a schematic flow chart illustrating a method for thermally processing a wafer according to an embodiment of the present invention;
FIG. 3 is a graph illustrating temperature variation in a heat treatment method for a wafer according to an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating a wafer without an oxide layer formed thereon;
FIG. 5 is a schematic diagram of the wafer and the support part during the formation of the oxide layer.
Reference numerals:
a wafer 10; an oxide layer 11;
a tray 20; a support portion 21.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
First, a method for heat-treating a wafer according to an embodiment of the present invention will be described in detail.
As shown in fig. 2 to 5, the method for thermally processing a wafer according to an embodiment of the present invention includes the following steps:
and step S1, placing the wafer in an inert atmosphere for pre-heat preservation treatment.
In some embodiments, in step S1, the temperature of the pre-incubation may be 450-. The pre-heat preservation treatment is carried out at a proper temperature, the temperature cannot be too high, the formation of oxygen nuclei can be reduced when the temperature is too high, the efficiency can be reduced when the temperature is too low, the cost is increased, the temperature of the pre-heat preservation treatment is 550 ℃, the time of the pre-heat preservation treatment can be 20-40min, the inert atmosphere is argon, preferably, the wafer can be placed in the argon, the pre-heat preservation treatment is carried out at 500 ℃ for 30min, and the pre-treatment is carried out at the pre-treatment temperature and time, so that interstitial oxygen can be diffused to the surface of the silicon wafer, the oxygen nuclei are well formed inside, a good DZ area can be formed, the treatment efficiency is high, and the cost is low.
Step S2, the pre-heat-preserved wafer is heated to a first temperature at a first heating rate.
In step S2, the process is performed under an inert atmosphere, the inert atmosphere is selected to be argon, the first temperature-raising rate can be 8-12 ℃/min, the first temperature can be 750-, can obtain excellent DZ area, reduce the deviation of sliding, production efficiency is high.
Step S3, the wafer is placed in the first oxidizing atmosphere, and the temperature is increased from the first temperature to a second temperature at a second temperature increasing rate, wherein the second temperature increasing rate is smaller than the first temperature increasing rate.
In step S3, the temperature-rising rate may be decreased to slowly rise the temperature, the atmosphere of the wafer is changed, the wafer is placed in a first oxidizing atmosphere, the first oxidizing atmosphere may be pure oxygen, the temperature is increased from the first temperature to the second temperature at a second temperature-rising rate, the second temperature-rising rate may be smaller than the first temperature-rising rate, the second temperature-rising rate is 1-3 ℃/min, the second temperature is 950-. The second heating rate is not too high, but considering that the production efficiency is affected by too low heating rate, therefore, the second heating rate is preferably selected to be 1-3 ℃/min, the second temperature is preferably selected to be 950-.
Step S4, the wafer is placed in a second oxidizing atmosphere, and the temperature is increased from the second temperature to a third temperature at a third temperature increasing rate, wherein the second temperature increasing rate is smaller than the third temperature increasing rate.
In step S4, the atmosphere of the wafer is changed, and the wafer is placed in a second oxidizing atmosphere, where the second oxidizing atmosphere may include oxygen and nitrogen, the second oxidizing atmosphere may be a mixed gas of nitrogen and oxygen, the volume ratio of nitrogen to oxygen may be 0.7:1 to 1.2:1, preferably, the volume ratio of nitrogen to oxygen is 1:1, the third temperature-raising rate may be 4-6 ℃/min, and the third temperature may be 1150-. In the temperature rise process, oxygen in the surface gaps can be further diffused, so that the surface cleanliness is improved, slip dislocation can be generated when the temperature rise rate is too high, the production efficiency is influenced when the temperature rise rate is too low, the production efficiency is reduced when the third temperature is too low, and the minority carrier lifetime is reduced; too high a third temperature will also produce slip dislocations. In the actual heat treatment process, the wafer may be placed on a fixture, as shown in fig. 4, the wafer 10 may be mounted on the support portion 21 of the tray 20 and then heat treated, and fig. 4 is a schematic view of the wafer without an oxide layer being formed; as shown in fig. 5, an oxide layer 11 is formed on the surface of the wafer device after two atmosphere changes, the oxide layer 11 is formed on both the surface of the wafer 10 and the support portion 21, the oxide layer 11 can prevent the support portion 21 from damaging the wafer 10, reduce pollution, effectively reduce slip dislocation, form the oxide layer 11 on the clamp of the wafer 10, and reduce pollution and damage to the wafer 10 caused by the wafer clamp. Meanwhile, metal impurities can diffuse to the oxide layer, and the oxide layer and impurities in the oxide layer can be removed in the cleaning step after the heat treatment.
Comprehensively considering that the volume ratio of nitrogen to oxygen in the second oxidizing atmosphere is 1:1, the temperature is increased from the second temperature to the third temperature 1150-1250 ℃ at a third temperature increasing rate of 4-6 ℃/min, the second temperature increasing rate is smaller than the third temperature increasing rate in the temperature increasing process, the first temperature increasing rate is larger than the third temperature increasing rate, preferably, the third temperature increasing rate is 5 ℃/min, the third temperature is 1200 ℃, the oxygen diffusion of the surface gap can be facilitated under the third temperature increasing rate and the atmosphere, an oxide layer 11 can be formed on the surfaces of the wafer and the clamp supporting part through two atmosphere changes, the pollution and the damage of the wafer clamp to the wafer 11 are reduced, the slip deviation is effectively reduced, and the surface cleanliness is improved.
And step S5, placing the wafer in an inert atmosphere and carrying out primary heat preservation at a third temperature.
In step S5, the atmosphere of the wafer is changed to an inert atmosphere, the wafer may be placed in argon gas to perform a first heat preservation at a third temperature, and the heat preservation time of the first heat preservation may be 30-60min, so that Fe ions in the internal gaps are diffused, the minority carrier lifetime is improved, the heat preservation time is reasonably selected, the heat preservation time is too short to be well diffused, the heat preservation time is too long to reduce the production efficiency, and slip dislocation is easily formed, therefore, the heat preservation time of the first heat preservation is preferably 40min, the production efficiency can be ensured by the above processing method, the minority carrier lifetime is prolonged, the Fe ion content can be reduced, and the slip deviation is small.
And step S6, cooling from the third temperature to the fourth temperature at different cooling rates after the primary heat preservation is finished, and performing secondary heat preservation.
According to some embodiments, in step S6, after the first heat preservation is completed, the temperature may be reduced from the third temperature to the fourth temperature at different cooling rates for performing the second heat preservation, the cooling process may be divided into a plurality of different cooling stages, the cooling rate of each cooling stage may be different, and the multi-stage cooling is favorable for generating a good DZ zone and a high-density BMD zone, so as to prolong the minority carrier lifetime and reduce the slip defect. The holding time of the secondary heat preservation can be no more than two hours, and the fourth temperature can be lower than the temperature of the pre-heat preservation treatment, for example, the fourth temperature can be 400 ℃, and the temperature of the pre-heat preservation treatment can be 500 ℃. Preferably, after the primary heat preservation is finished, the temperature can be reduced from the third temperature to the fifth temperature at the first temperature reduction rate, and then reduced from the fifth temperature to the fourth temperature at the second temperature reduction rate. The first temperature may be higher than the fifth temperature, the first temperature reduction rate may be higher than the second temperature reduction rate, for example, the first temperature reduction rate may be 8-12 ℃/min, the fifth temperature may be 650-.
The wafer can be slowly cooled in the second cooling stage, the second cooling rate can be smaller than the first cooling rate, and the wafer can be slowly cooled in the second cooling stage, so that the density of an internal BMD area can be increased, and therefore the wafer with a good DZ area, a high-density BMD area, a long minority carrier lifetime and few slip defects is obtained. The temperature reduction rate is as slow as possible, but considering the production cost, the second temperature reduction rate may be 1-5 deg.C/min, the fourth temperature may be 350 deg.C-450 deg.C, preferably, the second temperature reduction rate may be 3 deg.C/min, and the fourth temperature may be 400 deg.C. In the cooling stage, the temperature is reduced at different cooling rates in two stages, so that the slip dislocation can be effectively reduced, the generation of a good DZ zone and a high-density BMD zone is facilitated, the minority carrier lifetime is prolonged, the slip defect is reduced, and the production efficiency and the low cost can be ensured.
That is, in the wafer heat treatment method of the present invention, as shown in fig. 2, the wafer is first placed in an inert atmosphere for heat preservation, and then heated, the temperature rise stage is divided into three temperature rise stages, the temperature rise stages are sequentially heated at different temperature rise rates in the first, second, and third temperature rise stages, the silicon wafer is rapidly heated in the first and third temperature rise stages, the second temperature rise stage is slowly heated, the temperature is preserved after the temperature rise to a predetermined temperature, the annealing and cooling are performed after the heat preservation is finished, the rapid cooling is performed first, the slow cooling is performed, and then the temperature is preserved; and changing atmosphere in the heat treatment process, using inert atmosphere in the first temperature rise stage, using oxidizing atmosphere such as oxygen in the second temperature rise stage, and changing oxidizing atmosphere such as nitrogen and oxygen in the third temperature rise stage, wherein the third temperature rise stage and the third temperature rise stage are also performed in the inert atmosphere, and the wafer is subjected to heat treatment by controlling the temperature rise and temperature rise speed, the atmosphere, the temperature, the time and the like of the wafer, so that the content of interstitial Fe ions can be reduced, the minority carrier lifetime can be prolonged, the wafer with a high-density BMD region and a good DZ region can be obtained, and the slip defect caused by a device can be effectively prevented.
The invention also provides a wafer, which can be obtained by processing the wafer by using the heat treatment method in the above embodiment, and the specific heat treatment method can be referred to the heat treatment method in the above embodiment, which is not described herein again.
In order to better explain the heat treatment method of the wafer of the present invention, the heat treatment method of the wafer of the present invention is further described below with reference to some specific examples.
Example 1
Firstly, placing a wafer in argon gas in inert atmosphere for pre-heat preservation treatment, wherein the temperature of the pre-heat preservation treatment is 500 ℃, and the time is 30 min; heating the wafer subjected to the pre-heat preservation treatment to a first temperature of 800 ℃ at a first heating rate of 10 ℃/min; then the wafer is placed in oxygen in a first oxidizing atmosphere, and the temperature is increased from the first temperature of 800 ℃ to the second temperature of 1000 ℃ at a second temperature increasing rate of 3 ℃/min.
And placing the wafer in a second oxidizing atmosphere, wherein the second oxidizing atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of the nitrogen to the oxygen is 1:1, heating from the second temperature of 1000 ℃ to the third temperature of 1200 ℃ at a third heating rate of 5 ℃/min; and placing the wafer in argon gas in an inert atmosphere, and carrying out primary heat preservation at a third temperature of 1200 ℃, wherein the heat preservation time of the primary heat preservation is 40 min.
After the primary heat preservation is finished, firstly, the temperature is reduced from the third temperature of 1200 ℃ to the fifth temperature of 700 ℃ at the first cooling rate of 10 ℃/min, then, the temperature is reduced from the fifth temperature of 700 ℃ to the fourth temperature of 400 ℃ at the second cooling rate of 3 ℃/min, the heat preservation is carried out for 30min at the fourth temperature of 400 ℃, the heat treatment process can be shown in figure 1, and the wafer with the excellent DZ area and the high-density BMD area is obtained after the heat treatment.
Example 2
Firstly, placing a wafer in argon gas in inert atmosphere for pre-heat preservation treatment, wherein the temperature of the pre-heat preservation treatment is 450 ℃, and the time is 40 min; heating the wafer subjected to the pre-heat preservation treatment to a first temperature of 750 ℃ at a first heating rate of 8 ℃/min; then the wafer is placed in oxygen in a first oxidizing atmosphere, and the temperature is increased from the first temperature of 750 ℃ to the second temperature of 1050 ℃ at a second temperature-increasing rate of 3 ℃/min.
Placing the wafer in a second oxidizing atmosphere, wherein the second oxidizing atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of the nitrogen to the oxygen is 0.7:1, heating from 1050 ℃ at a third heating rate of 6 ℃/min to 1250 ℃ from the second temperature; and placing the wafer in argon gas in inert atmosphere, and carrying out primary heat preservation at a third temperature of 1250 ℃, wherein the heat preservation time of the primary heat preservation is 30 min.
And after the primary heat preservation is finished, firstly cooling from 1250 ℃ to 650 ℃ at a first cooling rate of 8 ℃/min, then cooling from 650 ℃ to 350 ℃ at a second cooling rate of 5 ℃/min, preserving heat at 350 ℃ for 60min, and obtaining the wafer with an excellent DZ area and a high-density BMD area after heat treatment.
Example 3
Firstly, placing a wafer in argon gas in inert atmosphere for pre-heat preservation treatment, wherein the temperature of the pre-heat preservation treatment is 550 ℃, and the time is 20 min; heating the wafer subjected to the pre-heat preservation treatment to a first temperature of 850 ℃ at a first heating rate of 12 ℃/min; then the wafer is placed in oxygen in a first oxidizing atmosphere, and the temperature is increased from the first temperature of 850 ℃ to the second temperature of 950 ℃ at a second temperature increasing rate of 1 ℃/min.
And placing the wafer in a second oxidizing atmosphere, wherein the second oxidizing atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of the nitrogen to the oxygen is 1.2:1, heating from the second temperature 950 ℃ to the third temperature 1150 ℃ at a third heating rate of 4 ℃/min; and (3) placing the wafer in argon gas in an inert atmosphere, and carrying out primary heat preservation at a third temperature of 1150 ℃, wherein the heat preservation time of the primary heat preservation is 60 min.
After the primary heat preservation is finished, firstly, the temperature is reduced from the third temperature of 1150 ℃ to the fifth temperature of 750 ℃ at the first cooling rate of 12 ℃/min, then, the temperature is reduced from the fifth temperature of 750 ℃ to the fourth temperature of 450 ℃ at the second cooling rate of 1 ℃/min, the heat preservation is carried out for 40min at the fourth temperature of 450 ℃, and the wafer with the excellent DZ area and the high-density BMD area is obtained after the heat treatment.
Example 4
Firstly, placing a wafer in argon gas in inert atmosphere for pre-heat preservation treatment, wherein the temperature of the pre-heat preservation treatment is 520 ℃, and the time is 30 min; heating the wafer subjected to the pre-heat preservation treatment to a first temperature 830 ℃ at a first heating rate of 12 ℃/min; then the wafer is placed in oxygen in a first oxidizing atmosphere, and the temperature is raised from the first temperature of 830 ℃ to the second temperature of 1050 ℃ at a second temperature-raising rate of 2 ℃/min.
And placing the wafer in a second oxidizing atmosphere, wherein the second oxidizing atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of the nitrogen to the oxygen is 1:1, heating from 1050 ℃ at a third heating rate of 5 ℃/min to 1180 ℃ at a third temperature; and placing the wafer in argon gas in an inert atmosphere, and carrying out primary heat preservation at a third temperature of 1180 ℃, wherein the heat preservation time of the primary heat preservation is 50 min.
And after the primary heat preservation is finished, firstly cooling from the third temperature 1180 ℃ to the fifth temperature 730 ℃ at a first cooling rate of 11 ℃/min, then cooling from the fifth temperature 730 ℃ to the fourth temperature 370 ℃ at a second cooling rate of 3 ℃/min, preserving heat at the fourth temperature 370 ℃ for 40min, and obtaining the wafer with the excellent DZ area and the high-density BMD area after heat treatment.
By the method of the embodiment, under the conditions of different temperature rising rates, atmospheres, temperature rising temperatures and heat preservation times, the wafer with long minority carrier lifetime, low interstitial iron ion content, excellent DZ area and high-density BMD area can be obtained after heat treatment.
According to the wafer heat treatment method, a wafer is placed in an inert atmosphere for pre-heat preservation, the wafer subjected to the pre-heat preservation is quickly heated to a first temperature, then the wafer is placed in a first oxidizing atmosphere and is slowly heated to a second temperature, the wafer is placed in a second oxidizing atmosphere and is quickly heated to a third temperature, the wafer is placed in the inert atmosphere and is subjected to primary heat preservation at the third temperature, and after primary heat preservation is finished, the wafer is cooled to a fourth temperature at different cooling rates for secondary heat preservation. By the method, the wafers in a DZ area and a high-density BMD area can be obtained, the minority carrier lifetime is prolonged, the content of interstitial iron ions is reduced, the pollution caused by devices is effectively prevented, the slippage problem caused by the devices can be controlled, the treatment effect on the wafers is improved, the treatment efficiency is improved, and the treatment cost is reduced.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for thermally processing a wafer, comprising the steps of:
step S1, placing the wafer in an inert atmosphere for pre-heat preservation treatment;
step S2, heating the wafer after the pre-heat preservation treatment to a first temperature at a first heating rate;
step S3, placing the wafer in a first oxidizing atmosphere, and heating from the first temperature to a second temperature at a second heating rate, wherein the second heating rate is smaller than the first heating rate;
step S4, placing the wafer in a second oxidizing atmosphere, and heating from the second temperature to a third temperature at a third heating rate, wherein the second heating rate is smaller than the third heating rate;
step S5, placing the wafer in an inert atmosphere and carrying out primary heat preservation at the third temperature;
and step S6, after the primary heat preservation is finished, the temperature is reduced from the third temperature to the fourth temperature at different temperature reduction rates, and secondary heat preservation is carried out.
2. The method as claimed in claim 1, wherein the first ramp rate is greater than the third ramp rate.
3. The method as claimed in claim 1, wherein in step S3, the first oxidizing atmosphere is oxygen; in step S4, the second oxidizing atmosphere includes oxygen and nitrogen.
4. The method as claimed in claim 1, wherein in step S6, after the primary heat-preservation is finished, the temperature is decreased from the third temperature to a fifth temperature at a first temperature-decreasing rate, and then decreased from the fifth temperature to the fourth temperature at a second temperature-decreasing rate.
5. The method as claimed in claim 4, wherein the first temperature is higher than the fifth temperature.
6. The method as claimed in claim 4, wherein the first temperature reduction rate is greater than the second temperature reduction rate.
7. The wafer thermal processing method as claimed in claim 4, wherein the first temperature-decreasing rate is 8-12 ℃/min, and the fifth temperature is 650-750 ℃;
the second temperature reduction rate is 1-5 ℃/min, and the fourth temperature is 350-450 ℃.
8. The method as claimed in claim 1, wherein the fourth temperature is lower than the temperature of the pre-soak process.
9. The wafer thermal processing method as claimed in claim 1, wherein in step S1, the temperature of the pre-heat-preservation treatment is 450-550 ℃, and the time of the pre-heat-preservation treatment is 20-40 min;
in step S2, the first temperature-increasing rate is 8-12 ℃/min, and the first temperature is 750-850 ℃;
in step S3, the second temperature-increasing rate is 1-3 ℃/min, and the second temperature is 950-1050 ℃;
in step S4, the third temperature-increasing rate is 4-6 ℃/min, and the third temperature is 1150-1250 ℃;
in step S5, the heat preservation time of the primary heat preservation is 30-60 min.
10. A wafer obtained by the heat treatment method for a wafer according to any one of claims 1 to 9.
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