JPH0778831A - Heat treatment - Google Patents

Abstract

PURPOSE:To improve resistance to hot electrons in, e.g. an MOS transistor, and form a shallow junction in a short time process, by heat-treating an object to be heated in the state that stress is not left in the object after heat treatment. CONSTITUTION:This method contains the following; a heating process for increasing the temperature of an object to be heated, a heat treatment process for keeping the object at a constant temperature (Ta), and a cooling process for decreasing the temperature of the object. In the heating process and/or the cooling process, the object is kept for a while at a temperature equal to or approximate to the transition point Tc. In other case, the object is kept in a specified temperature range passing the transition temperature Tc. Further, in another case, the temperature of the object passes the transition point Tc, at a heating speed or a cooling speed wherein the crystal structure of the object in the vicinity of the transition point Tc transfers from a stable state to another phase stable state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method, and more particularly to a heat treatment method in manufacturing a semiconductor device.

[0002]

2. Description of the Related Art As the integration scale of VLSI becomes 16M dynamic RAM, 4M static RAM, and further 64M dynamic RAM and 16M static RAM, the processing size becomes 0.5 μm to 0.35 μm.
Becomes smaller. As described above, the heat treatment technique has become important in the manufacturing process of the VLSI, which requires fine processing.

For example, in the activation annealing treatment, when the pattern processing dimension is changed from 0.5 μm to 0.35 μm,
The junction depth is also 0.15μm to 0.1μm
Therefore, it is necessary to set conditions so that the impurities ion-implanted with low energy do not cause redistribution.

In response to the above requirements, the heat treatment is being carried out at a low temperature. At the same time, various heat treatment methods such as laser annealing, heat treatment using incoherent light such as a halogen lamp or arc lamp, and heat treatment with a carbon strip heater have been developed.

Of the above, a short-time heat treatment method using incoherent light (RTP: Rapid Thermal Proce
ssing) is considered the most practical. An example thereof will be described below. In order to form a p ⁺ diffusion layer on a semiconductor substrate, boron difluoride (BF ₂ ⁺ ) is ion-implanted into a semiconductor substrate preamorphized with silicon ions,
RTP is performed to form an extremely shallow junction (for example, a junction depth of 0.
1 μm). For example, boron difluoride (BF ₂ ⁺ ) is used as the implanted ions, the ion implantation energy is 15 keV, and the dose amount is 2 P (peta) / cm 2.
^By setting to ² and performing ion implantation into the silicon substrate, and then performing RTP heating at 950 ° C. for 15 seconds,
A shallow pn junction of about 0.1 μm or less is obtained.

On the other hand, the impurities introduced into the silicon substrate for forming the n ⁺ diffusion layer have a high activation rate and a small diffusion coefficient, so that it is easy to obtain a shallow junction having a low resistance, for example, arsenic (As). ⁺ ) Is used. Arsenic is used as the impurity, the ion implantation energy is 60 keV, and the dose is 5
The specific resistance is 50Ω by performing ion implantation into the silicon substrate at a setting of P (peta) pieces / cm ² and then performing RTP for 10 seconds at about 1000 ° C. to 1100 ° C.
A shallow pn junction of ˜70 Ω / □ and a junction depth of about 0.15 μm or less is obtained.

[0007]

However, the above-mentioned R
In TP, since the temperature of the semiconductor substrate is rapidly raised or lowered, the phase state of silicon oxide becomes unstable. Therefore, for example, when a current stress is applied to the interface between the gate oxide film and the silicon substrate, the interface state is likely to occur, and the hot electron resistance is lower than that in the case of annealing in a normal diffusion furnace, for example. Become.

An object of the present invention is to provide a heat treatment method which is excellent in forming a shallow junction of a semiconductor device in a manufacturing process without lowering the reliability of the semiconductor device.

[0009]

SUMMARY OF THE INVENTION The present invention is a heat treatment method which is made to achieve the above object. That is, after performing a heating step of increasing the temperature of the object to be heat treated, a heat treatment method of holding the object to be heat treated at a constant temperature, and then performing a cooling step to lower the temperature of the object to be heat treated, In either one or both of the cooling steps, the object to be heat treated is temporarily held at a temperature at or near the transition point of the object to be heat treated.

Alternatively, when the temperature of the object to be heat treated is temporarily held at or near the transition point, the object to be heat treated is held within a predetermined temperature range passing through the transition point.

Alternatively, in the heating step, the crystal structure of the object to be heat treated is stable at a temperature higher than the transition point than the state where the crystal structure of the object to be heat treated is stable at a temperature lower than the transition point of the object to be heat treated. The temperature of the object to be heat-treated is increased at the heating rate of transition to the state.

Further, in the cooling step, the crystal structure of the object to be heat treated is stable at a temperature lower than the transition point than the state where the crystal structure of the object to be heat treated is stable at a temperature higher than the transition point of the object to be heat treated. The temperature of the object to be heat-treated is lowered at the cooling rate that shifts to the state.

[0013]

In the above heat treatment method, the heat treatment target is temporarily held at the transition point or a temperature in the vicinity of the transition point in one or both of the heating step and the cooling step, so that Since the crystal structure that is stable at a high temperature and is stable at a temperature lower than the transition point is smoothly changed, when the temperature of the heat-treated object returns to room temperature, stress is applied to the heat-treated object. It does not remain.

Alternatively, when the object to be heat treated is temporarily held at the transition point of the object to be heat treated or at a temperature in the vicinity thereof, by holding the object to be heat treated within a predetermined temperature range passing through the transition point, the same action as described above is achieved. Is obtained.

Alternatively, in the heating step, the crystal structure of the object to be heat-treated is stable from a state in which the crystal structure of the object to be heat-treated is stable at a temperature lower than the transition point of the object to be heat-treated. By raising the temperature of the object to be heat-treated at the heating rate of transition to the state, the same effect as above can be obtained.

In the cooling step, the crystal structure of the object to be heat treated is stable at a temperature higher than the transition point of the object to be heat treated, and the crystal structure of the object to be heat treated is stable at a temperature lower than the transition point. By lowering the temperature of the object to be heat-treated at the cooling rate that shifts to, the same effect as above can be obtained.

For example, when a semiconductor device having a silicon oxide film formed on a silicon substrate is annealed at a temperature of 900 ° C. or higher, for example, when the temperature of the semiconductor device rises or falls. , Pass through the transition point of silicon oxide (573 ° C., 870 ° C.). At this time,
If the temperature is slowly raised or lowered, the silicon oxide changes its crystal structure, that is, the temperature rises or falls with a volume change.

However, when the temperature is rapidly raised or lowered by RTP (eg RTA),
In particular, when the temperature is suddenly lowered, silicon oxide returns to room temperature with a stable crystal structure at a temperature higher than the transition point, so that stress remains in the silicon oxide film. Therefore, R
The hot electron resistance of the semiconductor device annealed in a normal diffusion furnace is higher than that of the semiconductor device annealed by TA.

Therefore, raising or lowering the temperature near the transition point is temporarily stopped and the temperature is maintained for a while, so that the crystal structure of silicon oxide is changed to a stable one at a low temperature. The same effect can be obtained by slowly increasing the temperature or decreasing the temperature in the vicinity of the transition point instead of temporarily stopping the temperature increase or the temperature decrease. However, when all the steps of increasing the temperature or all the steps of decreasing the temperature are performed slowly, the temperature increasing time or the temperature decreasing time becomes long, and it becomes difficult to obtain a shallow junction. For this reason, it is not possible to lengthen the time during which the temperature rise or temperature drop is temporarily stopped.

[0020]

EXAMPLE A first example of the present invention will be described with reference to the time chart shown in FIG. In the figure, the vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 1, in the heating step 1, an object to be heat treated (not shown) is heated from room temperature Tr at a heating rate Vh. Then, when the temperature of the object to be heat treated reaches the transition point Tc, the temperature is held at the transition point Tc for a predetermined time tkh. Alternatively, the temperature may be maintained near the transition point Tc. Subsequently, heating is performed to the heat treatment temperature Ta at the same heating rate Vh as above. The heating rate in the heating step 1 may be different before and after the transition point Tc. Then, the heat treatment step 2 is performed while maintaining the temperature at Ta for a predetermined time ta.

Then, the cooling step 3 is performed. In this step, the object to be heat treated is cooled at the cooling rate Vc. Then, when the temperature of the object to be heat treated reaches the transition point Tc, the temperature is held at the transition point Tc for a predetermined time tkc. Subsequently, the temperature of the object to be heat-treated is returned to, for example, the room temperature Tr by cooling at the same cooling rate Vc as described above. The cooling rate in the cooling step 3 may be different before and after the transition point Tc.

In the heat treatment method described with reference to FIG.
In one or both of the heating step 1 and the cooling step 3, the temperature is temporarily maintained at or near the transition point Tc of the object to be heat-treated, so that the heating step 1 stabilizes at a temperature lower than the transition point Tc. The crystal structure smoothly changes to a stable crystal structure at a temperature higher than the transition point resistance Tc. In the cooling step 3, the crystal structure that is stable at a temperature higher than the transition point Tc changes smoothly to the crystal structure that is stable at a temperature lower than the transition point resistance Tc. Therefore, when the temperature of the object to be heat treated returns to room temperature, no stress remains in the object to be heat treated.

As described above, it is preferable to hold the transition point Tc for a certain period of time Tkh or Tkc.
For example, with respect to the transition point Tc, an arbitrary temperature within a temperature range of, for example, ± 100 ° C. may be maintained for a certain period of time. Also in this case, when the temperature is returned to the room temperature Tr in the same manner as described above, almost no stress remains in the heat-treated body.

Next, the activation annealing treatment of the diffusion layer in the manufacturing process of the MOS transistor will be specifically described as an example. The purpose of the activation annealing treatment of the MOS transistor is to heat and activate the source / drain regions formed on the silicon substrate. During the annealing treatment, the gate insulation made of silicon oxide on the silicon substrate is used. The membrane is also heated at the same time. During the annealing treatment, the silicon oxide must pass through a transition point 573 ° C. at which low-temperature quartz is transformed into high-temperature quartz or vice versa, and a transition point 870 ° C. at which high-temperature quartz is transformed into tridymite or vice versa. become.

The annealing process will be described with reference to the time chart of the first example of the annealing process shown in FIG. In the figure, the vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 2, in the heating step 1, a semiconductor substrate (not shown) on which MOS transistors are formed is heated from room temperature (for example, 20 ° C.) at a heating rate of, for example, 100 ° C./sec. The temperature of the semiconductor substrate is 5 at the transition point.
After the temperature reaches 73 ° C., the transition point is maintained for 200 seconds, for example. Then, a heating rate similar to the above (for example, 10
0 ° C./sec), for example, to 1050 ° C. Then, in a heat treatment step 2, activation annealing is performed by holding the temperature at 1050 ° C. for 10 seconds.

Then, the cooling step 3 is performed. In this step, the semiconductor substrate is cooled at a cooling rate of 100 ° C./second, for example. Then, when the temperature of the semiconductor substrate reaches 573 ° C., the temperature is held at 573 ° C. for 200 seconds, for example. Then, at the same cooling rate (for example, 100 ° C./second) as described above, the temperature is returned to, for example, the above room temperature.

Silicon oxide also undergoes transformation even at 870 ° C. Therefore, an example of the annealing process in that case will be described with reference to the time chart of the second example of the annealing process shown in FIG. As shown in FIG. 3, in the heating step 1, the MOS is heated at a heating rate of, for example, 100 ° C./second from room temperature (for example, 20 ° C.).
A semiconductor substrate (not shown) having a transistor formed thereon is heated. Then, when the temperature of the semiconductor substrate reaches 870 ° C., it is held at 870 ° C. for 200 seconds, for example. Then, it is heated to, for example, 1050 ° C. at the same heating rate (for example, 100 ° C./second). Then, in the heat treatment step 2, 10
Activation annealing is performed by holding at 50 ° C. for 10 seconds.

Then, the cooling step 3 is performed. In this step, the semiconductor substrate is cooled at a cooling rate of 100 ° C./second, for example. Then, when the temperature of the semiconductor substrate reaches 870 ° C., this temperature state is maintained for 200 seconds, for example.
Then, at the same cooling rate as above (for example, 100 ° C./sec),
For example, the temperature is returned to the room temperature.

As described above, when the object to be heat treated is heated and annealed, and then returned to room temperature,
The process of holding at the transition point for a certain period of time when the temperature rises may be omitted, and the process of holding at the transition point for a certain period of time only during cooling may be performed.

The case where the temperature is maintained for a predetermined time at each transition point in the cooling step 3 will be described with reference to the time chart of the third example of the annealing treatment shown in FIG. As shown in FIG. 4, in the heating step 1, the annealing treatment temperature (for example, 1
050 ° C). Then, in the heat treatment step 2, the annealing temperature is maintained for a certain time (for example, 10 seconds).
Then, the cooling process 3 is performed. In this step, for example, 10
All transition points that pass when the temperature is lowered at a cooling rate of 0 ° C./sec (for example, when the gate insulating film is made of silicon oxide, the transition points of silicon oxide are 87).
0 ℃ and 573 ℃ each for a certain period of time (eg 200
Hold for 2 seconds.

An example of further shortening the annealing time is as follows:
This will be described with reference to the time chart of the fourth example of the annealing process shown in FIG. As shown in FIG. 5, after the heating step 1 and the heat treatment step 2 are performed, the cooling step 3 is performed in the same manner as described in FIG. In the cooling step 3, in the cooling step, holding is performed for about 200 seconds only at the transition point of 573 ° C. where the high temperature quartz is transformed into the low temperature quartz.

In each of the annealing treatments described above, in the heating step 1, the silicon oxide film smoothly changes from a stable crystal structure at a temperature lower than the transition point to a stable crystal structure at a temperature higher than the transition point. . Further, in the cooling step 3, the crystal structure that is stable at a temperature higher than the transition point is smoothly changed to the crystal structure that is stable at a temperature lower than the transition point. For this reason,
When the temperature of the silicon oxide film returns to room temperature, no stress remains in the silicon oxide film.

As described above, it is preferable to hold the transition point for a certain period of time.
Even if the silicon oxide film is returned to room temperature, no stress remains even if it is held at an arbitrary temperature within a temperature range of about ± 100 ° C. for a certain period of time.

Note that it is not necessary for the same heat treatment apparatus to hold the transition point for a certain period of time. One example thereof will be described with reference to the time chart of the fifth example of the annealing process shown in FIG. As shown in FIG. 6, in the cooling step 3, a transition point (for example, 5
When cooled to about 73 ° C.), the semiconductor substrate is transferred to another annealing treatment device (for example, a normal diffusion furnace). Then, the semiconductor substrate is annealed at the transition point for 20 minutes. After that, the temperature is returned to room temperature (for example, 20 ° C.) at a cooling rate of, for example, about 100 ° C./second. Alternatively, after the activation annealing treatment, the semiconductor substrate is cooled to a temperature below the transition point. Then, the semiconductor substrate may be heated to the transition point by another annealing apparatus and held for about 20 minutes, and then gradually cooled to room temperature (for example, 20 ° C.) at a cooling rate of about 100 ° C./sec. .

Next, as a second embodiment, when a gate insulating film formed on a semiconductor substrate is used as a heat-treated body, and is temporarily held at a temperature at or near the transition point of the gate insulating film in the cooling step, A case where the temperature is maintained in a predetermined temperature range passing through the transition point of the gate insulating film will be described with reference to the time chart of the second embodiment shown in FIG. In the figure,
The vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 7, in the heating step 1, the object to be heat treated (not shown) is heated from the room temperature Tr at the heating rate Vh. The temperature of the object to be heat treated is, for example, the heat treatment temperature Ta.
At that point, a heat treatment is performed to maintain that temperature for, for example, ta. This step is the heat treatment step 2.

Then, the cooling step 3 is performed. In this step, the object to be heat treated is cooled at the cooling rate Vc. Then, when the temperature of the object to be heat treated reaches a temperature Tc + ΔT which is higher than the transition point Tc by ΔT, for example, the object to be heat treated is held for a predetermined time tkc in a predetermined temperature range 2ΔT sandwiching the transition point Tc. Then, the temperature of the object to be heat treated is set to the cooling rate Vc.
Then, the temperature is returned to the room temperature Tr. The cooling rates before and after the transition point Tc do not have to be the same.

In the cooling step, the same effect as described in the first embodiment can be obtained by holding the object to be heat-treated for a predetermined time tkc within a predetermined temperature range 2ΔT that sandwiches the transition point Tc. The center temperature of the predetermined temperature range 2ΔT may not be the transition point Tc. It is sufficient that at least the transition point Tc is included in the temperature range.

Next, the case where the second embodiment is applied to the activation annealing treatment of the diffusion layer in the manufacturing process of the MOS transistor will be described with reference to the time chart of the annealing treatment example shown in FIG. In the figure, the vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 8, in the heating step 1, a semiconductor substrate (not shown) on which a MOS transistor is formed is heated from room temperature (for example, 20 ° C.) at a heating rate of, for example, 100 ° C./second. The temperature of the semiconductor substrate is, for example, 10
When the temperature reaches 50 ° C., the temperature is maintained for 10 seconds for activation annealing. The heat treatment step 2 is the time during which the activation annealing is performed.

Then, the cooling step 3 is performed. In this step, the semiconductor substrate is cooled at a cooling rate of 100 ° C./second, for example. The temperature of the semiconductor substrate is, for example, 583 ° C.
Then, the temperature is maintained in the temperature range of 20 ° C. for 20 seconds, for example. As a result, the temperature of the semiconductor substrate becomes 5 after 20 seconds.
It reaches 63 ° C. Then, the temperature is returned to approximately the same temperature as the room temperature, for example, at a cooling rate of 100 ° C./sec.

The above method is not limited to the case where the transition point is 573 ° C., but is, for example, 870 ° C.
As for the transition point, the same may be maintained for a predetermined time within a predetermined temperature that sandwiches the transition point. Further, in the above description, keeping in the predetermined temperature range is performed in the cooling step 3, but may be performed in the heating step 1, for example.

Next, the third embodiment will be described with reference to the time chart of the third embodiment shown in FIG. In the figure, the vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 9, in the heating step 1, room temperature T
The object to be heat treated (not shown) is heated at a heating rate Vh from r. Then, when the temperature of the object to be heat treated reaches a temperature Tc−ΔT which is lower than the transition point Tc by ΔT, for example, the heating rate of the object to be heat treated is set to a crystal structure of the object to be heat treated at a temperature lower than the transition point Tc. From the stable state to the transition point Tc
The heating is performed slowly at a heating rate Vsh at which the crystal structure of the heat-treated body transitions to a stable state at a higher temperature. Subsequently, when the temperature of the object to be heat treated reaches Tc + ΔT, the object to be heat treated is heated at the heating rate Vh. The heating rates before and after the transition point Tc may be different rates. Then, when the temperature of the object to be heat treated reaches the heat treatment temperature Ta, for example,
A heat treatment step 2 is performed in which the temperature is maintained for, for example, ta.

Then, the cooling step 3 is performed. In this step, the object to be heat-treated is cooled at the cooling rate Vc, for example. Then, when the temperature of the object to be heat treated reaches a temperature Tc + ΔT which is higher than the transition point Tc by ΔT, for example, the cooling rate of the object to be heat treated is higher than the transition point Tc and the crystal structure of the object to be heat treated is stable. The state is slowly cooled at a cooling rate Vsc at which the crystal structure of the heat-treated body transitions to a stable state at a temperature lower than the transition point Tc. After that, when the temperature passes through the transition point Tc and reaches a temperature Tc-ΔT that is lower than the transition point by ΔT, for example, the cooling rate is returned to Vc, and is returned to, for example, substantially the same temperature as the room temperature. The cooling rates before and after the transition point Tc may be different rates.

In the above heat treatment method, the heating rate Vsh and the cooling rate Vsc were set when passing through the transition point Tc in both the heating step 1 and the cooling step 3. In the case of the method, in the heating step 1, heating may be performed at the normal heating rate Vh to the heat treatment temperature Va, and the cooling rate may be Vsc when passing through the transition point Tc in the cooling step 3. Further, in the case where a film is formed on the object to be heat-treated at a high temperature, it is preferable to set the heating rate to Vsh when passing through the transition point Tc in the heating step 1.

Next, the case where the third embodiment is applied to the activation annealing treatment of the diffusion layer in the manufacturing process of the MOS transistor (not shown) will be described with reference to the time chart of the annealing treatment example shown in FIG. In the figure, the case where it is applied only to the cooling step 3 is shown. In the figure, the vertical axis represents temperature and the horizontal axis represents time.

As shown in FIG. 10, in the heating step 1, a semiconductor substrate (not shown) having a MOS transistor formed thereon is heated at a heating rate of, for example, 100 ° C./sec from room temperature (for example, 20 ° C.). The temperature of the semiconductor substrate is, for example, 10
When the temperature reaches 50 ° C., the temperature is maintained for 10 seconds for activation annealing. This annealing process is the heat treatment process 2.

Then, the cooling step 3 is performed. In this step, the semiconductor substrate is cooled at a cooling rate of 100 ° C./second, for example. The temperature of the semiconductor substrate is, for example, 583 ° C.
At that time, the cooling rate is changed from the stable state of the crystal structure of the silicon oxide at a temperature higher than the transition point of the silicon oxide forming the gate insulating film to the crystal structure of the silicon oxide at a temperature lower than the transition point. Is slowly cooled at a cooling rate of, for example, about 1 ° C./sec. The state is maintained for 20 seconds, for example. That is, the semiconductor substrate is cooled at a cooling rate of 1 ° C./sec until the temperature of the semiconductor substrate passes through the transition point 573 ° C. and reaches 563 ° C. Then, the temperature is returned to approximately the same temperature as the room temperature, for example, at a cooling rate of 100 ° C./sec.

In the annealing process described with reference to FIG.
The crystal structure of silicon oxide smoothly changes from high temperature quartz having a stable crystal structure to low temperature quartz having a stable crystal structure.
Therefore, no stress remains in the silicon oxide when the temperature of the silicon oxide returns to room temperature.

Further, the above cooling method is not limited to the case where the transition point is 573 ° C., for example, when the transition point of 870 ° C. is passed through the transition point in the same manner as above. The same effect can be obtained if the cooling rate of is set to a slow rate that stably changes the crystal structure. Furthermore, in the above description, the cooling step 3 has been described as an example, but for example, in the heating step as well, the heating rate when passing through the transition point is
If you use a slow speed that stably changes the crystal structure,
Similar effects are obtained.

As described above, the heat treatment method described in each of the above-described embodiments is applied to the case where the heat-treated body formed of a material having a transition point in at least the temperature range of the cooling step is heat-treated and returned to the original temperature. When applied, no residual stress remains in the heat-treated object after the heat treatment. Further, it can be similarly applied to the case of heat-treating an object to be heat-treated which includes a transition point in the above temperature range and is formed of a material having a different transition point. No residual stress remains in each of the latter materials.

The numerical values used in the above description are merely examples, and may be appropriately selected depending on the material, size, etc. of the object to be heat-treated (including annealing).

[0056]

As described above, according to the present invention,
In either or both of the heating step or the cooling step, the temperature of the transition point of the object to be heat treated or the vicinity thereof,
Since the object to be heat treated is temporarily held, it is possible to shift from a stable crystal structure to a stable crystal structure of another phase. Therefore, no stress remains in the object to be heat treated. Alternatively, when temporarily holding the temperature at or near the transition point of the object to be heat treated, the object to be heat treated is held in a predetermined temperature range passing through the transition point. Absent. Further, when passing through the transition point in the heating step or the cooling step, since heating or cooling is performed at a heating rate or a cooling rate at which a stable crystal structure transitions to a stable crystal structure of another phase, the heat treatment target is treated in the same manner as above Does not leave any stress. Therefore, in any of the above heat treatment methods, no stress remains in the object to be heat treated, and thus high hot electron resistance can be obtained as in a semiconductor device heat-treated in a normal diffusion furnace. Therefore, the reliability of the semiconductor device can be improved.

Since this heat treatment method can be applied to heat treatment for a short time, it becomes possible to form a diffusion layer having a shallow junction.
Therefore, it is possible to improve the element performance, and
High integration of elements can be achieved.

[Brief description of drawings]

FIG. 1 is a time chart of a first embodiment.

FIG. 2 is a time chart of a first example of an annealing process.

FIG. 3 is a time chart of a second example of annealing treatment.

FIG. 4 is a time chart of a third example of annealing treatment.

FIG. 5 is a time chart of a fourth example of annealing treatment.

FIG. 6 is a time chart of a fifth example of the annealing process.

FIG. 7 is a time chart in the second embodiment.

FIG. 8 is a time chart of an example of annealing treatment.

FIG. 9 is a time chart in the third embodiment.

FIG. 10 is a time chart of an example of annealing treatment.

[Explanation of symbols]

 1 heating process 2 heat treatment process 3 cooling process Tc transition point Vsh heating rate Vsc cooling rate

Claims (4)

[Claims] 1. A heat treatment in which a heating step of raising the temperature of the object to be heat treated is performed, a heat treatment step of holding the object to be heat treated at a constant temperature is performed, and then a cooling step of lowering the temperature of the object to be heat treated is performed. In the method, the heat treatment method is characterized in that, in either one or both of the heating step and the cooling step, the object to be heat treated is temporarily held at a temperature at or near the transition point of the object to be heat treated. 2. The heat treatment method according to claim 1, wherein, in either or both of the heating step and the cooling step, the temperature of the object to be heat treated is temporarily held at or near the transition point, A heat treatment method characterized by holding in a predetermined temperature range passing through the transition point. 3. The heat treatment method according to claim 2, wherein the heating step is performed at a temperature lower than a transition point of the object to be heat-treated and a temperature higher than the transition point from a state where the crystal structure of the object to be heat-treated is stable. In the heat treatment method, the transition point is passed at a heating rate at which the crystal structure of the heat treated body transitions to a stable state. 4. The heat treatment method according to claim 2, wherein the cooling step is performed at a temperature higher than a transition point of the object to be heat-treated and from a state where a crystal structure of the object to be heat-treated is stable to a temperature lower than the transition point. In the heat treatment method, the transition point is passed at a cooling rate at which the crystal structure of the object to be heat treated transitions to a stable state.