阅读说明：本技术 硅晶片的热处理方法 (Method for heat treatment of silicon wafer ) 是由 潮田彩 青木龙彦 于 2019-10-10 设计创作，主要内容包括：本发明提供硅晶片的热处理方法,在惰性气体气氛下的硅晶片的热处理中,该热处理方法可有效地进行在硅晶片表面的自然氧化膜溶解时所产生的SiO气体的排气,可抑制反应产物在热处理腔室内的堆积,防止滑移的恶化。在900℃以上且1100℃以下的温度区段中保持晶片5秒以上且30秒以下的时间,同时将晶片转速设为80rpm以上且120rpm以下,控制腔室内的惰性气体的供给,使气体置换率成为90%以上。(The invention provides a heat treatment method of a silicon wafer, which can effectively exhaust SiO gas generated when a natural oxide film on the surface of the silicon wafer is dissolved in the heat treatment of the silicon wafer in an inert gas atmosphere, can inhibit the accumulation of reaction products in a heat treatment chamber, and can prevent the deterioration of slip. The wafer is held in a temperature range of 900 ℃ to 1100 ℃ for a time period of 5 seconds to 30 seconds, and the supply of the inert gas in the chamber is controlled so that the gas substitution rate becomes 90% or more by setting the wafer rotation speed to 80rpm to 120 rpm.)

1. A method for heat treatment of a silicon wafer, characterized in that: which is a heat treatment method of a silicon wafer for performing a rapid temperature rise and fall heat treatment of a silicon wafer held rotatably in a chamber under an inert gas atmosphere,

wherein the wafer is held in the chamber at a temperature range of 900 ℃ to 1100 ℃ for a time of 5 seconds to 30 seconds while the wafer is rotated at 80rpm to 120rpm,

the supply of the inert gas in the chamber is controlled so that the gas replacement rate becomes 90% or more.

2. The heat treatment method for silicon wafers as set forth in claim 1, wherein: before the heat treatment temperature in the chamber reaches 1300 ℃ or higher, the wafer is held in a temperature range of 900 ℃ to 1100 ℃ for a period of 5 seconds to 30 seconds, and the wafer rotation speed is set to 80rpm to 120 rpm.

3. The heat treatment method for a silicon wafer as set forth in claim 1 or 2, characterized in that: in the temperature range of 900 ℃ to 1100 ℃, the pressure in the chamber is set to 1kPa or less.

Technical Field

The present invention relates to a method for heat treatment of a silicon wafer, and more particularly, to a method for heat treatment of a silicon wafer in an inert atmosphere, which can efficiently exhaust SiO gas generated when a natural oxide film on the surface of the silicon wafer is dissolved and prevent SiO in a heat treatment chamber_xA method for heat-treating a solid deposited silicon wafer.

Background

With the high integration of semiconductor devices, semiconductor substrates such as silicon wafers (hereinafter, also simply referred to as "wafers") are required to have high quality. In particular, it is essential to reduce crystal defects in the active region where the device (device) is formed. For example, a silicon wafer is manufactured by growth and various processes of a silicon single crystal, but crystal defects occurring at the growth stage of the single crystal remain in the processed wafer.

As a method for reducing crystal defects remaining in the silicon wafer by the short-time heat treatment, as disclosed in patent document 1, for example, a method using an rtp (rapid Thermal process) apparatus (rapid Thermal processing apparatus) is known. Patent document 1 discloses a method in which a silicon wafer is heated in the RTP apparatus at a temperature range of 1300 ℃ or higher and silicon melting point or lower in an argon atmosphere, then cooled to a temperature of 400 ℃ or higher and 800 ℃ or lower, and then switched to an oxygen atmosphere, and heat-treated at a temperature of 1250 ℃ or higher and silicon melting point or lower.

However, when the heat treatment is performed in an argon atmosphere, a natural oxide film formed on the wafer surface is dissolved and is released as SiO gas. The generated SiO gas is not exhausted completely, and the silicon surface is etched by gas at high temperature, and SiO is formed on the inner wall of the chamber or other component surface at low temperature_xThe solid forms are stacked. Further, the above SiO_xThe solid has the following problems: which becomes a cause of particles adhering to the wafer in the heat treatment.

In addition, in general, in a single wafer type heat treatment apparatus, while a silicon wafer being treated is measured at a plurality of points on the back surface of the wafer using a noncontact radiation thermometer or the like, the treatment temperature is controlled, but in the above-mentioned SiO_xWhen the reaction product is deposited on the radiation thermometer, there is a problem that accurate temperature measurement cannot be performed, the wafer temperature during processing becomes uneven, and a slip defect occurs.

For the above-mentioned problems based on the reaction product from the SiO gas, patent document 2 discloses the following method: a gas flow is generated in the space between the silicon wafer and the radiation thermometer, and the deposition rate of the reaction product on the radiation thermometer is reduced.

Patent document 3 describes: by rotating the wafer at a high speed (for example, 250 to 350rpm) to some extent, the reaction product is not accumulated on the wafer, and the slip defect is suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-29429;

patent document 2: japanese Kokai publication Hei-2002-507250;

patent document 3: japanese patent laid-open publication No. 2011-233556.

Disclosure of Invention

Problems to be solved by the invention

However, in the method disclosed in patent document 2, even if the amount of the reaction product deposited on the radiation thermometer can be reduced, the deposition cannot be completely suppressed.

In addition, although the method described in patent document 3 is effective for suppressing the deposition of reaction products on the wafer, there are problems as follows: since it is difficult to exhaust the SiO gas generated by the detachment of the natural oxide film from the chamber, if the treatment is continuously performed, the SiO gas is discharged from the chamber_xAnd the reaction products may accumulate in the chamber.

Under such circumstances, the present inventors have intensively studied and found that: when the silicon wafer is subjected to heat treatment while being rotated under an inert gas atmosphere, the temperature is controlled to 1300 ℃ or higherThe wafer rotation speed and gas replacement rate in the temperature zone (900-1100 deg.C) of SiO gas generated from the wafer surface are controlled, the exhaust efficiency of SiO gas from the thermal processing chamber is improved, and SiO gas is prevented from being exhausted from the thermal processing chamber_xAnd the accumulation of the reaction product in the chamber, thereby completing the present invention.

An object of the present invention is to provide a heat treatment method of a silicon wafer, which can effectively perform the exhaust of SiO gas generated when a natural oxide film on the surface of the silicon wafer is dissolved, suppress the accumulation of reaction products in a heat treatment chamber, and prevent the deterioration of slip in the heat treatment under an inert gas atmosphere for reducing crystal defects remaining in the silicon wafer in a short time.

Means for solving the problems

The method for heat treatment of a silicon wafer according to the present invention, which has been proposed to solve the above problems, has the following features: the method is a method for heat-treating a silicon wafer by rapidly raising and lowering the temperature of the silicon wafer in a chamber in an inert gas atmosphere, wherein the wafer is held in the chamber at a temperature range of 900 ℃ to 1100 ℃ for a period of 5 seconds or longer, and the inert gas is supplied to the chamber so that the gas substitution rate is 90% or more while the wafer rotation speed is 80rpm to 120 rpm.

It is desirable that the wafer is held in a temperature range of 900 to 1100 ℃ for a time period of 5 to 30 seconds while the wafer is rotated at 80 to 120rpm before the heat treatment temperature in the chamber reaches 1300 ℃ or higher.

Further, it is desirable that the pressure in the chamber is 1kPa or less in a temperature range of 900 ℃ to 1100 ℃.

When a silicon wafer is heat-treated in an inert gas atmosphere by such a heat treatment method, the SiO gas generated when the natural oxide film on the wafer surface is dissolved can be effectively exhausted by controlling the wafer rotation speed and the gas replacement rate in the chamber. As a result, the accumulation of the reaction product in the heat treatment chamber can be suppressed, and the deterioration of the slip can be prevented.

Effects of the invention

According to the present invention, there can be provided a heat treatment method of a silicon wafer, which can efficiently perform the exhaust of SiO gas generated when the natural oxide film on the surface of the silicon wafer is dissolved in the heat treatment of the silicon wafer in an inert gas atmosphere, suppress the accumulation of reaction products in the heat treatment chamber, and prevent the deterioration of slip.

Drawings

FIG. 1 is a sectional view of an RTP apparatus to which a heat treatment method for a silicon wafer according to the present invention is applied.

FIG. 2 is a graph showing the sequence of the heat treatment method of a silicon wafer according to the present invention.

Fig. 3 is a graph showing the results of the embodiment according to the present invention.

Fig. 4 is another graph showing the results of the embodiment according to the present invention.

Fig. 5 is another graph showing the results of the embodiment according to the present invention.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an outline of an RTP apparatus used for the method for heat-treating a silicon wafer according to the present invention.

As shown in fig. 1, an RTP apparatus 10 used in the method for heat-treating a silicon wafer according to the present invention includes: a chamber (reaction tube) 20 having an atmosphere gas inlet 20a and an atmosphere gas outlet 20b, a plurality of lamps 30 disposed apart from an upper portion of the chamber 20, and a wafer support 40 for supporting the wafer W in a reaction space 25 in the chamber 20. Although not shown, a rotation mechanism is provided for rotating the wafer W around its central axis at a predetermined speed.

The wafer support 40 includes: a ring-shaped base (susceptors) 40a for supporting the outer periphery of the wafer W, and a stage (stage)40b for supporting the base 40 a. The chamber 20 is made of quartz, for example. The lamp 30 is constituted by a halogen lamp, for example. The susceptor 40a is made of, for example, silicon. The stage 40b is made of, for example, quartz.

When the RTP apparatus 10 shown in fig. 1 is used to perform RTP on a wafer W, the wafer W is introduced into the reaction space 25 from a wafer introduction port, not shown, provided in the chamber 20, and is supported on the susceptor 40a of the wafer support 40. Then, an atmosphere gas described later is introduced from the atmosphere gas introduction port 20a, and the lamp 30 irradiates the surface of the wafer W while rotating the wafer W by a rotation mechanism not shown.

In the RTP apparatus 10, the temperature in the reaction space 25 is controlled by measuring the average temperature of a plurality of points (for example, 9 points) in the wafer surface in the wafer radial direction at the lower portion of the wafer W by a plurality of radiation thermometers 50 embedded in the stage 40b of the wafer support 40, and controlling a plurality of halogen lamps 30 based ON the measured temperature (individual ON-OFF control of each lamp, control of the light emission intensity of the emitted light, or the like).

Next, a method for heat treatment of a silicon wafer according to the present invention will be described with reference to the drawings.

The heat treatment method of a silicon wafer according to the present invention is a method of performing RTP on a silicon wafer obtained by slicing a silicon single crystal ingot grown by a Czochralski method (Czochralski method) under predetermined production conditions.

The growth of a silicon single crystal ingot based on the Czochralski method is carried out by a known method.

That is, polycrystalline silicon filled in a quartz crucible is heated to form a silicon melt, a seed crystal is brought into contact with the silicon melt from above the liquid surface, the seed crystal and the quartz crucible are pulled while being rotated, and the diameter of the seed crystal is increased to a desired diameter to grow a straight tube portion, thereby producing a silicon single crystal ingot.

The silicon single crystal ingot thus obtained is processed into a silicon wafer by a known method.

That is, after a silicon single crystal ingot is sliced into a wafer shape by an inner peripheral blade, a wire saw, or the like, a silicon wafer is manufactured through processing steps such as chamfering (chamfering), polishing (lapping), etching (etching), and grinding (grinding) of an outer peripheral portion. The processing steps described herein are exemplary steps, and the present invention is not limited to these processing steps.

Next, the manufactured silicon wafer is subjected to RTP using predetermined manufacturing conditions.

Fig. 2 is a conceptual view showing a heat treatment sequence of RTP suitable for the heat treatment method of a silicon wafer according to the present invention.

The heat treatment sequence in RTP applied to the heat treatment method for a silicon wafer according to the present invention is such that the produced silicon wafer is set in a chamber 20 held at a desired temperature T0 (for example, 500 ℃) in an RTP apparatus 10 shown in fig. 1.

An atmosphere gas (e.g., argon gas) is introduced into the chamber 20 from the atmosphere gas inlet port 20a to form an inert gas atmosphere.

Then, the inside of the chamber 20 is heated by the halogen lamp 30, and the temperature is rapidly raised at a predetermined rate until reaching a temperature range T1 of 900 ℃ to 1100 ℃ shown in the graph of fig. 2.

Here, the temperature range T1 is controlled to maintain the temperature range for a predetermined time tp1 (preferably, 5 seconds or more and 30 seconds or less). The heating pattern (pattern) before exceeding the temperature range T1 may mainly adopt patterns 1, 2, and 3, for example, as shown in fig. 2.

Further, in order to facilitate the discharge of the SiO gas from the heat treatment space, the gas pressure in the chamber in the temperature zone T1 is controlled to be 1kPa or less.

The reason why the temperature section T1 is 900 ℃ or more and 1100 ℃ or less is that: if the temperature range T1 is higher than 1100 ℃, although the natural oxide film on the wafer surface can be removed, the SiO gas instantaneously etches the silicon surface when the temperature is kept too high. If the temperature range T1 is less than 900 ℃, the temperature for sufficiently decomposing the native oxide film is not reached, and the native oxide film on the wafer surface cannot be sufficiently removed.

The reason why the time tp1 for holding the temperature range T1 is set to be 5 seconds or more and 30 seconds or less is that: although the natural oxide film thickness formed on the surface of the wafer W varies among wafers, a sufficient effect can be obtained when the retention time tp1 is 5 seconds or more. Further, by setting the holding time tp1 to 30 seconds or less, the probability of particles adhering to the surface of the wafer W can be suppressed to a low level.

The rotation speed of the wafer W in the temperature zone T1 is controlled to 80rpm to 120 rpm.

Further, since there is a possibility that the SiO gas cannot be sufficiently exhausted when the amount of the inert gas to be introduced is insufficient, the inert gas is introduced at a flow rate (30L/min to 100L/min) at which 90% or more of the gas in the chamber can be replaced within 1 minute.

Thus, when SiO gas is generated from the surface of the wafer W by dissolution of the natural oxide film, the SiO gas discharge efficiency can be improved.

When the gas replacement ratio is 90%, it is desirable to reduce the pressure in the chamber, specifically, 10kPa or less. In particular, if the pressure in the chamber is set to 1kPa or less, the gas replacement ratio can be set to 90% within 5 seconds, and the object of the present invention can be achieved more effectively.

When the rotation speed of the wafer W is set to be lower than 80rpm, there may be a problem that the temperature of the wafer W in the plane becomes uneven, and the wafer W during the treatment warps and falls off the susceptor 40 a.

On the other hand, if the rotation speed of the wafer W is set to be higher than 120rpm, the exhaust efficiency of the SiO gas is lowered, the SiO gas tends to stay directly above and below the wafer, and if the SiO gas remains at a high temperature exceeding 1100 ℃, the silicon surface is etched instantaneously, and thus a reaction product is disadvantageously deposited in the processing chamber.

After the predetermined time tp1, if the temperature in the chamber 20 exceeds the temperature range T1, the temperature is rapidly raised to T2 (preferably 1300 ℃) at a predetermined temperature raising rate, and is maintained for 30 seconds, for example.

Then, after the temperature was decreased to T3 (for example, 600 ℃) at a predetermined temperature decrease rate, the inside of the chamber was changed to an oxidizing atmosphere.

When the inside of the chamber is switched to the oxidizing atmosphere, the temperature is raised to T4 (e.g., 1250 ℃) at a predetermined temperature raising rate and held for 30 seconds, and then the temperature is lowered to T5 (e.g., 600 ℃) at a predetermined temperature lowering rate, thereby ending the RTP.

As described above, according to the embodiment of the present invention, when the silicon wafer is heat-treated in the inert gas atmosphere, the SiO gas generated when the natural oxide film on the wafer surface is dissolved can be effectively exhausted by controlling the wafer rotation speed and the gas replacement rate in the chamber. As a result, the accumulation of the reaction product in the heat treatment chamber can be suppressed, and the deterioration of the slip can be prevented.

In the above embodiment, the example of the inert gas is argon gas, but the present invention can be applied to a case where another inert gas is introduced into the chamber.

Examples

The heat treatment method of a silicon wafer according to the present invention will be further described with reference to examples. In this example, the following experiment was performed according to the above embodiment.

In this embodiment, the following RTP apparatus of a single chip system is used: the wafer held horizontally in the chamber is heated by a lamp from the front surface side thereof, and the temperature of the wafer is measured by a radiation thermometer from the back surface side thereof while controlling. In this RTP apparatus, 1000 to 1500 single-crystal silicon double-side polished wafers having a diameter of 300mm were subjected to heat treatment, and changes in the oxide film thickness and changes in the slip length (measured by an X-ray topography method) of the wafers were evaluated.

As a general heat treatment condition, the chamber was set to an argon atmosphere, the temperature was rapidly raised to 1300 ℃ and held for 30 seconds, and then the temperature was lowered to 600 ℃, and after switching to an oxidizing atmosphere, the temperature was rapidly raised to 1250 ℃ and held for 30 seconds without taking out the wafer from the chamber.

The conditions in the chamber were set for each of the examples and comparative examples in the following manner. The temperature range T1 (c) shown under the following conditions is a temperature range at the timing (timing) corresponding to the temperature range T1 in the graph of fig. 2.

(a) Temperature section T1 (. degree. C.);

(b) wafer rotation speed (rpm) in temperature section T1;

(c) a holding time or a temperature rise time (seconds) in the temperature section T1;

(d) gas replacement ratio (%) in the temperature section T1;

(e) pressure (kPa) in the temperature section T1.

As shown in tables 1 and 2, examples 1 to 13 and comparative examples 1 to 6 were set according to the conditions (a) to (e) and evaluated.

In the decision column of Table 1, A (Excellent) indicates that no increase in oxide film thickness was observed in the continuous treatment and SiO in the chamber was not observed_xSignificant build-up of reaction products. B (good) indicates that although SiO is not seen in the chamber_xAlthough the reaction product was significantly deposited, a trouble such as the wafer dropping off from the susceptor was observed in the heat treatment. C (defect) indicates that an increase in oxide film thickness and occurrence of slip were observed as the number of wafers processed increased.

In table 2, the influence of the pressure (kPa) in the chamber on the time until the gas substitution rate became 90% or more was evaluated.

[ Table 1]

[ Table 2]

As shown in example 10 of table 1, if the holding time in the temperature zone T1 becomes longer (45 seconds), the probability of particles adhering to the wafer surface increases, and although not significant, SiO in the chamber is seen_xAccumulation of reaction product (judgment B). Therefore, it was confirmed that the holding time in the temperature section T1 is desirably 30 seconds or less.

As shown in comparative example 4 of table 1, when the holding temperature was high (1150 ℃), the natural oxide film on the wafer surface could be removed, but when the holding temperature was too high, the silicon surface was instantaneously etched by the generated SiO gas (decision C). Therefore, it was confirmed that the holding temperature is desirably 1100 ℃ or lower.

Further, as shown in comparative example 3 of Table 1, when the holding temperature is low (850 ℃ C.), the natural oxide film on the wafer surface cannot be sufficiently removed (judgment C). This is believed to be due to: the temperature for sufficiently dissolving the natural oxide film is not reached. Therefore, it was confirmed that the holding temperature is desirably 900 ℃ or higher.

In view of the above results, it is confirmed from table 1 that: when the temperature in the chamber is 900 ℃ to 1100 ℃, it is desirable that the wafer rotation speed is 0rpm to 120rpm (preferably 80rpm to 120 rpm), the holding time at this time is 5 seconds to 30 seconds, and the gas replacement rate is 90% or more.

In addition, it was also confirmed that: when the gas substitution rate is 90% as shown in table 2, the gas substitution rate can be set to 90% within 5 seconds by setting the chamber internal pressure to 1kPa or less, and the object of the present invention can be more effectively achieved.

In example 1, comparative example 1, and comparative example 2 shown in table 1, changes in the number of adhered particles (number per wafer) of more than 60nm, total slip length (mm), and oxide film thickness increase rate (%) with respect to the number of wafers processed are shown in the graphs of fig. 3, fig. 4, and fig. 5, respectively.

In the graph of fig. 3, the horizontal axis represents the number of processed wafers, and the vertical axis represents the number of adhered particles (number/wafer). As shown in the graph, the number of adhered particles increased as the number of treated pieces increased in comparative examples 1 and 2, but the number of adhered particles was suppressed to a low level without being limited by the number of treated pieces in example 1.

In the graph of fig. 4, the horizontal axis represents the number of processed pieces, and the vertical axis represents the total slip length (mm). As shown in the graph, although the slip was significantly generated in comparative examples 1 and 2, no slip was generated at all in example 1.

In the graph of fig. 5, the horizontal axis represents the number of processed wafers, and the vertical axis represents the rate of increase (%) of oxide film thickness. As shown in the graph, in comparative examples 1 and 2, the oxide film thickness increased with an increase in the number of wafers, but in example 1, the rate of increase in the oxide film thickness was suppressed to a low level.

As described above, according to the present invention, it was confirmed that: the SiO gas generated when the natural oxide film on the surface of the silicon wafer is dissolved can be effectively exhausted, the accumulation of reaction products in the heat treatment chamber can be suppressed, and the deterioration of the slip can be prevented.

Description of the symbols

10: an RTP device;

20: a chamber;

20 a: an atmosphere gas inlet;

20 b: an atmosphere gas discharge port;

25: a reaction space;

30: a lamp;

40: a wafer support.