JPH08250504A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To prevent impurities from entering a substrate in an intrinsic gettering process by carrying out intrinsic/gettering process comprised of a first heat treatment process to a third heat treatment process of various specific conditions with a silicon nitride film provided to a silicon board surface. CONSTITUTION: An about 1500Å-thick nitride film 2 is deposited by a CVD method after a heat oxide film for preventing a surface of a substrate 1 from being roughened is formed and a first heat treatment is carried out for one hour at about 900 to 1350 deg.C. Then, oxygen contained in a surface of the substrate 1 passes through a nitride film 2 and is diffused, and a denuded layer 3 is formed in a surface of the substrate 1 and an intrinsic point defect generation region 4 is formed in an inside thereof. Thereafter, when second (400 to 650 deg.C) and third (900 to 1350 deg.C for 0 to 5 hours) heat treatments are carried out, oxygen precipitation nucleus is formed in an intrinsic point defect generation region 4 and an oxygen precipitation is formed. Metallic impurities are prevented from entering following a heat treatment process by providing a nitride film 2 to a surface of the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, an intrinsic gettering (IG) step and a well forming step both of which are performed before forming an element region on a semiconductor substrate. Thus, the present invention relates to a method for manufacturing a semiconductor device in which the processing steps are shortened.

[0002]

2. Description of the Related Art Conventionally, a silicon single crystal substrate used as a semiconductor wafer contains supersaturated impurity oxygen, and this impurity oxygen precipitates in the substrate as silicon oxide in a heat treatment step to cause a precipitation defect. It is known that intrinsic gettering is a phenomenon in which these precipitation defects form gettering metal impurities such as heavy metal elements mixed in the substrate.

This intrinsic gettering is positively used in the actual manufacturing process of semiconductor elements, but when precipitation defects are present in the element region, it causes deterioration of semiconductor element characteristics. It is also known to become.

Therefore, in order to improve such inconvenience, when the intrinsic gettering step is performed, the intrinsic gettering step is performed by a multi-step heat treatment step so that the deposition position of oxygen precipitates on the substrate is increased. Is controlled accurately.

Here, the conventional intrinsic
The gettering process will be described with reference to FIGS. 8 and 9.
Note that FIG. 8 is a time chart of the intrinsic gettering process, in which the vertical axis represents the processing temperature (° C.) and the horizontal axis represents the processing time in hours. FIG. 9 shows the outline of the intrinsic gettering process.

Referring to FIGS. 8 and 9 (a), first, a silicon substrate 1 as a substrate to be processed is placed in a heat treatment furnace kept at a temperature of 750.degree.
By increasing the temperature to 1200 ° C. at a temperature increase rate of in (minutes) and performing heat treatment at this temperature for 1 hour (step 1: first heat treatment step), oxygen contained in the surface of the silicon substrate 1 is diffused outward. , A defect-free layer (Denu
ded zone) 3 is formed.

In this case, inside the silicon substrate 1, the nuclei of precipitates of oxygen atoms contained in the silicon substrate 1 are decomposed and oxygen becomes an atomic state, and its movement becomes extremely free. An intrinsic point defect generation region 4 including an extremely large number of intrinsic point defects due to oxygen atoms is formed inside.

Next, referring to FIGS. 8 and 9B, the silicon substrate 1 is subjected to 6 at a temperature decreasing rate of 4 ° C./min.
After the temperature is decreased to 00 ° C. (step 2), heat treatment is performed at this temperature for 6 hours (step 3: second heat treatment step),
Inside the silicon substrate 1, oxygen precipitation nuclei, which is a composite of oxygen and intrinsic point defects, are precipitated to form the oxygen precipitation nuclei generation region 5.

Next, referring to FIGS. 8 and 9C, the silicon substrate 1 is subjected to 1 at a temperature rising rate of 3 ° C./min.
After the temperature is raised to 100 ° C. (step 4), heat treatment is performed at this temperature for 1 hour (step 5: third heat treatment step) to grow oxygen precipitate nuclei inside the silicon substrate 1 to form an oxygen precipitate precipitate region 6. To do.

Referring to FIGS. 8 and 9D, when a DRAM (dynamic random access memory) is formed on the silicon substrate 1,
Impurities are ion-implanted by using the mask 7 provided on the silicon substrate 1 to form the peripheral circuit, and the implanted ions are activated at 10 ° C. for 10 minutes to drive in.
A well region 8 is formed by performing a heat treatment process for well formation for a certain period of time.

In the high temperature heat treatment step such as the well forming step, metal impurities such as Fe, Cr, Cu, or Na resulting from a furnace jig, a quartz jig such as a wafer basket, or a furnace heater member are oxygen. Gettering will occur in the precipitation nuclei or oxygen precipitates.

The first heat treatment step in the intrinsic gettering step is performed at 1000 ° C. or higher, the second heat treatment step is performed at 600 to 800 ° C., and the third heat treatment step is 1000 ° C. or higher. It is done in.

[0013]

However, the conventional intrinsic gettering process requires a long time of 15 hours or more (15.5 hours in FIG. 8).
Since a high temperature heat treatment of 5 hours or more (10 hours in FIG. 8) is performed for the well formation step in the DRAM manufacturing method, the long heat treatment step at the beginning of this process is problematic in terms of productivity and production cost. Has become.

Further, although the metal impurities are gettered by the oxygen precipitation nuclei formed in the intrinsic gettering step or the oxygen precipitates, the metal impurities newly enter in the high temperature treatment step for a long time and the semiconductor is infiltrated. This also causes deterioration of the device, which causes a problem that the manufacturing yield decreases.

Accordingly, the present invention is an intrinsic
It is an object of the present invention to shorten a high temperature heat treatment step including a gettering step and prevent metal impurities from entering a silicon substrate during the heat treatment.

[0016]

FIG. 1 is a time chart of a manufacturing process of a semiconductor device showing a principle configuration of the present invention, and a means for solving the problem in the present invention will be described with reference to FIG. To do.

See FIG. 1 (1) In the method of manufacturing a semiconductor device according to the present invention, a step of depositing a silicon nitride film on a silicon substrate, a first heat treatment step of isothermally heat treating the silicon substrate at 900 to 1350 ° C., and a silicon A second heat treatment step of isothermally heat-treating the substrate at 400 to 650 ° C., 900 to 1350 for the silicon substrate.
A third heat treatment step of performing isothermal heat treatment at 0 ° C. for 5 hours, and a heat treatment step of forming an impurity diffusion region in the silicon substrate, and at least part of the first to third heat treatment steps and impurity diffusion in the silicon substrate. It is characterized in that it is performed also as a heat treatment step of forming a region.

Further, the present invention is characterized in that in the method of manufacturing a semiconductor device described in (1) above, a silicon oxide film having a thickness of 20 Å or more is formed on a silicon substrate prior to the deposition of the silicon nitride film. .

(2) Further, in the present invention, in the method for manufacturing a semiconductor device according to the above (1), the temperature lowering rate in the temperature lowering step between the first heat treatment step and the second heat treatment step is 15 ° C./minute or less, In addition, the temperature rising rate between the second heat treatment step and the third heat treatment step is set to 15 ° C./min or less, and a part of the third heat treatment step and the impurity diffusion region in the silicon substrate are performed. Is also performed as a heat treatment step for forming.

Further, the present invention is characterized in that in the method of manufacturing a semiconductor device described in (2), at least one of the first heat treatment step and the second heat treatment step is performed for 30 minutes or more.

(3) In addition, the present invention provides the intermediate heat treatment in which the silicon substrate is isothermally heat-treated at 600 to 900 ° C. between the second heat treatment step and the third heat treatment step in the method (2) for manufacturing a semiconductor device. In addition to providing the steps, the temperature raising rate in the temperature raising step between the second heat treatment step and the intermediate heat treatment step and in the temperature raising step between the intermediate heat treatment step and the third heat treatment step is set to 15 ° C./min or less. Characterize.

Further, the present invention is characterized in that in the method of manufacturing a semiconductor device according to (3), at least one of the first heat treatment step, the second heat treatment step and the intermediate heat treatment step is performed for 30 minutes or more. .

(4) Further, in the present invention, in the method for manufacturing a semiconductor device according to (1), impurities are ion-implanted in the silicon substrate between the step of depositing a silicon nitride film on the silicon substrate and the first heat treatment step. There is a step of injecting,
The temperature decrease rate in the temperature decrease step between the first heat treatment step and the second heat treatment step is 15 ° C./minute or less, and the temperature increase rate in the temperature increase step between the second heat treatment step and the third heat treatment step is 15 C./minute or less, and at least part of the first heat treatment step and the heat treatment step of forming the impurity diffusion region in the silicon substrate are performed.

Further, the present invention is characterized in that in the semiconductor device manufacturing method of (4), at least one of the isothermal heat treatments of the first heat treatment step and the second heat treatment step is performed for 30 minutes or more.

(5) Further, the present invention is the method of manufacturing a semiconductor device according to the above (4), in which the silicon substrate is subjected to an isothermal heat treatment at 600 to 900 ° C. between the second heat treatment step and the third heat treatment step. The heat treatment step is provided, and the temperature raising rate in the temperature raising step between the second heat treatment step and the intermediate heat treatment step and in the temperature raising step between the intermediate heat treatment step and the third heat treatment step is 15 ° C./min or less. Is characterized by.

Further, the present invention is characterized in that in the semiconductor device manufacturing method of (5), at least one of the first heat treatment step, the second heat treatment step, and the intermediate heat treatment step is performed for 30 minutes or more. .

[0027]

In the method of manufacturing a semiconductor device of the present invention, the first
By performing the intrinsic gettering process including the heat treatment process to the third heat treatment process in a state where the silicon nitride film 2 is provided on the surface of the silicon substrate 1, the metal in the silicon substrate 1 is externally supplied in the intrinsic gettering process. It is possible to prevent impurities and the like from entering.

This situation will be described with reference to FIG. Note that FIG. 2A is a cross-sectional view of an essential part of the silicon substrate 1 on which the intrinsic gettering process of the present invention is completed, and FIG. 2B is a silicon substrate on which the intrinsic gettering process is not performed. (Non-IG processing), a silicon substrate that has been subjected to intrinsic gettering processing without a silicon nitride film (non-IG processing)
FIG. 9 is a diagram showing a non-defective product rate of an oxide film breakdown voltage when a diode is formed on a substrate (nitrided film IG process: equivalent to the present invention) on which a silicon nitride film is provided and an intrinsic gettering process is performed.

2A, when the intrinsic gettering process is performed by providing the silicon nitride film 2 on the surface of the silicon substrate 1, the defect-free layer extends from the surface of the silicon substrate 1 to the depth d of about 30 μm. 3, and an oxygen precipitate precipitation region 6 is formed inside the silicon substrate 1 thereunder.

In this case, although the silicon nitride film 2 serving as an oxidation resistant film is present on the surface of the silicon substrate 1, it means that outward diffusion of oxygen has occurred. It is judged that the oxygen in the substrate 1 becomes an oxygen atom state and becomes free to move, and the oxygen atom, that is, O ₂ is not transmitted, but the oxygen atom is transmitted.

Further, referring to FIG. 2B, the ratio of the non-defective oxide film withstand voltage of the diode provided on each silicon substrate 1 is examined. In the case of the silicon substrate 1 (intrinsic gettering process not performed) (IG-free process). Although it is about 45%, in the case of the silicon substrate 1 (non-nitrided film IG processing) which has been subjected to the intrinsic gettering processing without providing the silicon nitride film 2, the non-defective rate is about 20 to 35%. Yes, the rate of non-defective products is significantly reduced as compared with the non-IG process.

On the other hand, in the case of the substrate on which the silicon nitride film 2 is provided and the intrinsic gettering process is performed (nitride film IG process), it is confirmed that the yield rate is improved to about 55 to 70%. From these results, in the intrinsic gettering process, metal impurities may enter from the furnace core tube, the quartz jig, the heater of the furnace, or the like. However, when the silicon nitride film 2 is provided, It is judged that the silicon nitride film 2 serves as a barrier against metal impurities and does not enter the silicon substrate 1.

Further, by performing a part of the first heat treatment step to the third heat treatment step and the heat treatment step of forming the impurity diffusion region in the silicon substrate 1, the heat treatment step at the initial stage of the process can be shortened. .

In addition, the first heat treatment step is performed at 900 to 135
By the isothermal heat treatment at 0 ° C., oxygen contained in the surface of the silicon substrate 1 is outwardly diffused to form a defect-free layer 3 on the surface.
And the intrinsic point defect generation region 4 can be formed inside the silicon substrate 1.

Further, the second heat treatment step is carried out at 400 to 650.
The oxygen precipitation nucleus generation region 5 can be formed inside the silicon substrate 1 by performing the isothermal heat treatment at ℃, and further, by performing the third heat treatment at the isothermal heat treatment at 900 to 1350 ° C., the silicon substrate 1 can be formed. An oxygen precipitate precipitation region 6 can be formed inside.

By forming a silicon oxide film having a thickness of 20 Å or more on the silicon substrate 1 prior to the deposition of the silicon nitride film 2, it is possible to reduce the roughness of the surface of the silicon substrate 1.

Further, the temperature lowering rate in the temperature lowering step between the first heat treating step and the second heat treating step is set to 15 ° C./minute or less, and the temperature raising step between the second heat treating step and the third heat treating step is performed. By setting the rate of temperature rise during the heating to 15 ° C./minute or less, it is possible to prevent the fine precipitates that have been deposited from disappearing due to dissociation, and further, to carry out impurity diffusion in part of the third heat treatment step and the silicon substrate 1. The heat treatment step can be shortened by performing the heat treatment step for forming the region as well.

Further, by providing an intermediate heat treatment step for isothermally heat-treating the silicon substrate 1 at 600 to 900 ° C. between the second heat treatment step and the third heat treatment step, the temperature rising rate up to the third heat treatment step can be increased. And the third heat treatment step can be shortened.

Further, a step of ion-implanting impurities into the silicon substrate 1 is provided between the step of depositing the silicon nitride film 2 on the silicon substrate 1 and the first heat treatment step, and the first heat treatment step and the silicon substrate 1 are formed. By also performing the heat treatment step of forming the impurity diffusion region, the heat treatment time can be shortened, and the third heat treatment step can also be shortened.

When a step of ion-implanting impurities into the silicon substrate 1 is provided between the step of depositing the silicon nitride film 2 on the silicon substrate 1 and the first heat treatment step,
By providing an intermediate heat treatment step of isothermally heat-treating the silicon substrate 1 at 600 to 900 ° C. between the second heat treatment step and the third heat treatment step, the temperature rising rate up to the third heat treatment step can be increased, In addition, the third heat treatment step can be shortened.

In the method of manufacturing each semiconductor device described above, at least one of the first heat treatment step and the second heat treatment step or the intermediate heat treatment step is performed for 30 minutes or more, whereby outward diffusion and oxygen precipitation nuclei are generated. Formation or precipitation of oxygen precipitates can be carried out to a minimum.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 3 shows an outline of the intrinsic gettering step, and FIG. 4 shows a time chart of the intrinsic gettering step, in which the treatment temperature (° C.) is plotted on the vertical axis. The horizontal axis indicates the processing time in units of time.

3 (a) and FIG. 4 First, a 500 Å thermal oxide film (not shown) for thermally oxidizing the silicon substrate 1 having an impurity oxygen concentration of 30 ppm to prevent the surface of the silicon substrate 1 from being roughened. After forming
A silicon nitride film 2 having a thickness of 1500 Å is deposited by the CVD method, and then the silicon substrate 1 provided with the thermal oxide film and the silicon nitride film 2 is housed in a heat treatment furnace kept at a temperature of 750 ° C. 10 ° C / m in N ₂ atmosphere
By increasing the temperature to 1200 ° C. at a temperature increase rate of in (minutes) and performing heat treatment at this temperature for 1 hour (step 2: first heat treatment step), oxygen contained in the surface of the silicon substrate 1 is diffused outward. The defect-free layer 3 (Denu
ded zone).

Although the temperature of the first heat treatment step in the example is 1200 ° C., it is not limited to this value, and if the temperature is low, the outward diffusion is small and the defect-free layer is hard to be formed on the surface. If the temperature is too high, the melting point of silicon approaches and the crystallinity of the substrate deteriorates.
Is preferably in the range of 1050 to 1350 ° C., and more preferably 1050-1
The range of 250 ° C. is more preferable.

In this case, since the oxygen contained in the silicon substrate 1 becomes extremely free to move, the oxygen existing on the surface of the silicon substrate 1 permeates the silicon nitride film 2 provided on the surface of the silicon substrate 1 and is removed from the outside. Can be diffused.
In the silicon substrate 1, an intrinsic point defect generation region 4 including an extremely large number of intrinsic point defects caused by oxygen atoms is formed as in the conventional intrinsic gettering step.
Is formed.

3 (b) and FIG. 4 Next, the silicon substrate 1 is subjected to 5 ° C. at a temperature decreasing rate of 4 ° C./min.
After the temperature is lowered to 00 ° C. (step 3), heat treatment is performed at this temperature for 3 hours (step 4: second heat treatment step),
Inside the silicon substrate 1, oxygen precipitation nuclei which are a composite of oxygen and an intrinsic point defect are deposited to form an oxygen precipitation nuclei generation region 5.

The temperature of the second heat treatment step is not limited to 500.degree. C. As the heat treatment is carried out at a lower temperature, a larger number of nuclei of oxygen precipitates (fine precipitates) can be formed and the gettering ability can be enhanced. Therefore, the temperature may be in the range of 400 to 650 ° C, more preferably in the range of 450 to 550 ° C, and the second heat treatment time can be further shortened by adopting a low temperature.

3 (c) and FIG. 4, the silicon substrate 1 is then subjected to 1 at a temperature rising rate of 4 ° C./min.
The temperature is raised to 100 ° C. (step 5), oxygen precipitate nuclei are grown to form an oxygen precipitate precipitation region 6 (step 6: third heat treatment step), and immediately up to 750 ° C. at a temperature decrease rate of 4 ° C./min. The temperature is lowered (step 7).

The third heat treatment step in this case is substantially 0 hour, but it may be performed for 0 to 5 hours, and the longer the time, the greater the amount of oxygen precipitates deposited, so gettering. Although the action is enhanced, the processing time is prolonged and the productivity is reduced.

The temperature of this third heat treatment step is 110.
The temperature is not limited to 0 ° C., but may be in the range of 900 to 1350 ° C., more preferably in the range of 1000 to 1150 ° C., and the precipitation of oxygen precipitates may be reduced at low temperatures, while at high temperatures. After that, the precipitated oxygen precipitates are dissociated and reduced.

Next, a mask 7 is provided on the silicon substrate 1, impurities are selectively introduced by ion implantation using the mask 7, and then the silicon substrate 1 is heat-treated again. And a well region 8 is formed by performing a heat treatment process at 1100 ° C. for 10 hours in order to activate and drive in the implanted ions. In this well region 8, for example, a peripheral circuit of DRAM is formed.

The silicon nitride film 2 used in the intrinsic gettering step is used as the mask 7 in the ion implantation step or as the mask in the selective oxidation step (LOCOS step) for element isolation or the like. The selective oxidation process may be performed after forming the well region 8 or may be performed simultaneously.

Since the oxygen precipitates can be increased by the heat treatment step associated with the well formation after the intrinsic gettering step, the treatment time of the third heat treatment step can be shortened. For example, in the case of FIG. 21.6 hours (11.6 hours for the intrinsic gettering step and 10 hours for the well forming step), and 25.5 hours (15 hours for the intrinsic gettering step) of the conventional example of FIG. The processing time can be shortened as compared with 0.5 hours and the well forming step is 10 hours. It should be noted that the reduction of the time of the second heat treatment step also greatly contributes to the reduction of the processing time.

In the first embodiment, the temperature lowering rate and the temperature raising rate in the temperature lowering step and the temperature raising step are 4 ° C.
/ Min, but it is not limited to this value, and each may be 15 ° C./min or less. If this speed is low, there is a problem that the treatment time is too long, while if it is too high, oxygen precipitation nuclei are generated. Since problems such as dissociation occur, a range of 3 to 6 ° C / min is more preferable, for example. The first heat treatment step to the third heat treatment step in the first embodiment are all performed in a N ₂ atmosphere at normal pressure.

Next, with reference to FIG. 5, a manufacturing process of the second embodiment of the present invention will be described. In the following description, the reference numerals shown in FIG. 3 are borrowed for easy understanding of each component.

Referring to FIG. 5, first, a silicon substrate 1 having an impurity oxygen concentration of 30 ppm is thermally oxidized to form a 500 Å thermal oxide film on the surface thereof to prevent the surface of the silicon substrate 1 from being roughened, and then a thickness of 1500 Å is formed by a CVD method. is a silicon nitride film 2 is deposited, then after accommodating the silicon substrate 1 provided with the thermal oxide film and a silicon nitride film 2 to the heat treatment furnace that is maintained at a temperature of 750 ° C., in an N ₂ atmosphere at normal pressure 10 By increasing the temperature to 1200 ° C. at a temperature increasing rate of ° C./min and performing heat treatment at this temperature for 1 hour (step 2: first heat treatment step), oxygen contained in the surface of the silicon substrate 1 is diffused outward. A defect-free layer 3 is formed on the surface of the silicon substrate 1. Further, in the inside of the silicon substrate 1, as in the first embodiment, an intrinsic point defect generation region 4 including an extremely large number of intrinsic point defects caused by oxygen atoms is formed.

The temperature of the first heat treatment step is 1200 ° C.
However, the temperature is not limited to this value.If the temperature is low, there is little outward diffusion and it becomes difficult to form a defect-free layer on the surface.If the temperature is too high, the melting point of silicon approaches and the crystallinity of the substrate decreases. Therefore, the range of 900 to 1350 ° C. is preferable, and the range of 1050 to 1250 ° C. is more preferable.

Next, the silicon substrate 1 is cooled to 500 ° C. at a temperature lowering rate of 4 ° C./min (step 3) and then heat-treated at this temperature for 2 hours (step 4: second heat treatment step), whereby the silicon substrate 1 Oxygen precipitation nuclei, which are composites of oxygen and intrinsic point defects, are deposited inside the inside of the to form oxygen precipitation nuclei generation region 5.

The temperature of the second heat treatment step is not limited to 500 ° C., and as the heat treatment is performed at a lower temperature, a large number of nuclei of oxygen precipitates (fine precipitates) can be formed and the gettering ability can be enhanced. Therefore, the temperature may be in the range of 400 to 650 ° C, more preferably in the range of 450 to 550 ° C, and the second heat treatment time can be further shortened by adopting a low temperature.

Then, the silicon substrate 1 is heated to 700 ° C. at a heating rate of 5 ° C./min (step 5) and heat-treated at this temperature for 1 hour (step 6: intermediate heat treatment step) to form fine oxygen precipitates. Is increased to a certain degree, the silicon substrate 1 is heated again to 1100 ° C. at a heating rate of 5 ° C./min (step 7), and oxygen precipitates are further grown to form oxygen precipitate precipitation regions 6 ( Step 8: Third heat treatment step), immediately lowering the temperature to 750 ° C. at a temperature lowering rate of 4 ° C./min (step 9).

The third heat treatment step in this case is substantially 0 hour, but it may be performed for 0 to 5 hours, and the longer the time, the greater the amount of oxygen precipitates deposited, so gettering. Although the action is enhanced, the processing time is prolonged and the productivity is reduced.

The temperature of this third heat treatment step is 110.
The temperature is not limited to 0 ° C., but may be in the range of 900 to 1350 ° C., more preferably in the range of 1000 to 1150 ° C., and the precipitation of oxygen precipitates may be reduced at low temperatures, while at high temperatures. After that, the precipitated oxygen precipitates are dissociated and reduced.

Next, a mask 7 is provided on the silicon substrate 1, impurities are selectively introduced by ion implantation using the mask 7, and then the silicon substrate 1 is placed in a heat treatment furnace again to implant the implanted ions. A well region 8 is formed by performing a heat treatment process at 1100 ° C. for 10 hours for activation and drive-in.
A peripheral circuit of the DRAM is formed in.

Even in this case, the intrinsic
The silicon nitride film 2 used in the gettering step can be used as the mask 7 in the ion implantation step or the mask in the selective oxidation step for element isolation or the like, and is selected after the well region 8 is formed. The oxidation step may be performed or may be performed simultaneously.

Since the oxygen precipitates can be increased by the well forming step after the intrinsic gettering step, the processing time of the third heat treatment step can be shortened. For example, in the case of FIG. 21.1 hours (11.1 hours for the intrinsic gettering step and 10 hours for the well forming step), and the processing time can be shortened as compared with 25.5 hours of the conventional example of FIG. .

Further, although the intermediate heat treatment step in the second embodiment is 700 ° C., it is not limited to this value, but may be in the range of 600 to 900 ° C., and further in the range of 650 to 750 ° C. Is more preferable, and by adopting this intermediate heat treatment step, dissociation of fine oxygen precipitates can be suppressed even if the temperature rising rate up to the subsequent third heat treatment step is increased. This greatly contributes to the reduction of the processing time and the overall processing time.

In the second embodiment, the temperature lowering rate and the temperature raising rate in the temperature lowering step and the temperature raising step are 4 to 4.
Although it is 5 ° C./min, it is not limited to this value, and it may be 15 ° C./min or less in each case. If this rate is too low, it takes a long time to process, while if too high, oxygen precipitation occurs. Since a problem such as dissociation of nuclei occurs, for example, the temperature decreasing rate in step 3 and step 9 is 3 to
A range of 10 ° C./min is more preferable, and Step 5
And the heating rate of the step 7 is preferably 5 to 10 ° C./min. The first heat treatment step to the third heat treatment step and the intermediate heat treatment step in the second embodiment are all performed under normal pressure N ₂
It is done in an atmosphere.

Next, the manufacturing process of the third embodiment of the present invention will be described with reference to FIG. In the following description, the reference numerals shown in FIG. 3 are borrowed for easy understanding of each component.

Referring to FIG. 6, first, a silicon substrate 1 having an impurity oxygen concentration of 30 ppm is thermally oxidized to form a 500 Å thermal oxide film (not shown) on the surface to prevent the surface of the silicon substrate 1 from being roughened.
A 1500 Å-thick silicon nitride film 2 is deposited by the CVD method, and then impurities for forming wells are ion-implanted.

Next, after the ion-implanted silicon substrate 1 was placed in a heat treatment furnace kept at a temperature of 750 ° C.,
12 at a temperature rising rate of 10 ° C / min in a N ₂ atmosphere at normal pressure
By raising the temperature to 00 ° C. and performing heat treatment at this temperature for 10 hours (step 3: first heat treatment step), oxygen contained in the surface of the silicon substrate 1 is outwardly diffused to form a defect-free layer on the surface of the silicon substrate 1. 3 and the silicon substrate 1
The well region 8 is formed by activating and driving in the ions implanted in the.

The temperature of the first heat treatment step is 1200 ° C.
However, the temperature is not limited to this value.If the temperature is low, there is little outward diffusion and it becomes difficult to form a defect-free layer on the surface.If the temperature is too high, the melting point of silicon approaches and the crystallinity of the substrate decreases. Therefore, the range of 900 to 1350 ° C. is preferable, and the range of 1050 to 1250 ° C. is more preferable.

Next, the silicon substrate 1 is cooled to 500 ° C. at a temperature lowering rate of 4 ° C./min (step 4) and then heat-treated at this temperature for 3 hours (step 5: second heat treatment step), whereby the silicon substrate 1 is processed. Oxygen precipitation nuclei, which are composites of oxygen and intrinsic point defects, are deposited inside the inside of the to form oxygen precipitation nuclei generation region 5.

The temperature of the second heat treatment step is not limited to 500 ° C., and as the heat treatment is performed at a lower temperature, a large number of nuclei of oxygen precipitates (fine precipitates) can be formed, and the gettering ability can be improved. Therefore, the temperature may be in the range of 400 to 650 ° C, more preferably in the range of 450 to 550 ° C, and the second heat treatment time can be further shortened by adopting a low temperature.

Next, the silicon substrate 1 is heated to 1100 ° C. at a temperature rising rate of 4 ° C./min (step 6), and heat-treated at this temperature for 1 hour (step 7: third heat treatment step) to form oxygen precipitates. After forming the precipitation layer, the temperature is lowered to 750 ° C. at a temperature lowering rate of 4 ° C./min (step 8).

Even in this case, the intrinsic
The silicon nitride film 2 used in the gettering step can be used as a mask in the selective oxidation step for element isolation or the like. After the intrinsic gettering step is completed, the silicon nitride film 2 is used for selective oxidation. You may perform a process.

The third heat treatment step in this case is 1 hour, but it may be performed for 0 to 5 hours as in the second embodiment. The longer the time, the more the amount of oxygen precipitates is deposited. Although the gettering effect is increased because the number of the elements increases, the processing time becomes longer and the productivity is reduced.

The temperature of this third heat treatment step is 110.
The temperature is not limited to 0 ° C., but may be in the range of 900 to 1350 ° C., more preferably in the range of 1000 to 1150 ° C., and the precipitation of oxygen precipitates may be reduced at low temperatures, while at high temperatures. After that, the precipitated oxygen precipitates are dissociated and reduced.

In the third embodiment, the time for the first heat treatment step can be saved by performing both the first heat treatment step and the well forming step, and the time for the second heat treatment step can be reduced. By shortening, for example, in the case of FIG. 6, the total becomes 21.6 hours, which is 2 times that of the conventional example of FIG.
The processing time can be shortened as compared with 5.5 hours.

Further, in the first embodiment, the temperature lowering rate and the temperature raising rate in the temperature lowering step and the temperature raising step are 4 ° C.
/ Min, but it is not limited to this value, and each may be 15 ° C./min or less. If this speed is low, there is a problem that the treatment time is too long, while if it is too high, oxygen precipitation nuclei are generated. Since problems such as dissociation occur, a range of 3 to 6 ° C / min is more preferable, for example. The first to third heat treatment steps in the third embodiment are all performed in a normal pressure N ₂ atmosphere.

Next, the manufacturing process of the fourth embodiment of the present invention will be described with reference to FIG. In the following description, the reference numerals shown in FIG. 3 are borrowed for easy understanding of each component.

Referring to FIG. 7, first, a silicon substrate 1 having an impurity oxygen concentration of 30 ppm is thermally oxidized to form a 500 Å thermal oxide film (not shown) on the surface to prevent the surface of the silicon substrate 1 from being roughened.
A 1500 Å-thick silicon nitride film 2 is deposited by the CVD method, and then impurities for forming wells are ion-implanted.

Next, after the ion-implanted silicon substrate 1 was placed in a heat treatment furnace maintained at a temperature of 750 ° C.,
12 at a temperature rising rate of 10 ° C / min in a N ₂ atmosphere at normal pressure
By raising the temperature to 00 ° C. and performing heat treatment at this temperature for 10 hours (step 3: first heat treatment step), oxygen contained in the surface of the silicon substrate 1 is outwardly diffused to form a defect-free layer on the surface of the silicon substrate 1. 3 and the silicon substrate 1
The well region 8 is formed by activating and driving in the ions implanted in the.

The temperature of the first heat treatment step is 1200 ° C.
However, the temperature is not limited to this value.If the temperature is low, there is little outward diffusion and it becomes difficult to form a defect-free layer on the surface.If the temperature is too high, the melting point of silicon approaches and the crystallinity of the substrate decreases. Therefore, the range of 900 to 1350 ° C. is preferable, and the range of 1050 to 1250 ° C. is more preferable.

Next, the silicon substrate 1 is cooled to 500 ° C. at a temperature lowering rate of 4 ° C./min (step 4) and then heat-treated at this temperature for 2 hours (step 5: second heat treatment step), whereby the silicon substrate 1 Oxygen precipitation nuclei, which are composites of oxygen and intrinsic point defects, are deposited inside the inside of the to form oxygen precipitation nuclei generation region 5.

The temperature of the second heat treatment step is not limited to 500 ° C., and as the heat treatment is performed at a lower temperature, a large number of nuclei of oxygen precipitates (fine precipitates) can be formed, and the gettering ability can be enhanced. Therefore, the temperature may be in the range of 400 to 650 ° C, more preferably in the range of 450 to 550 ° C, and the second heat treatment time can be further shortened by adopting a low temperature.

Then, the silicon substrate 1 is heated to 700 ° C. at a heating rate of 5 ° C./min (step 6) and heat-treated at this temperature for 1 hour (step 7: intermediate heat treatment step) to form fine oxygen precipitates. After increasing the temperature to some extent, the silicon substrate 1 is again heated to 1100 ° C. at a heating rate of 5 ° C./min (step 8), and heat-treated at this temperature for 1 hour (step 9: third heat treatment step) to obtain oxygen. Precipitate After forming a deposit layer, 4 ℃
The temperature is decreased to 750 ° C. at a temperature decrease rate of / min (step 10).

Even in this case, the intrinsic
The silicon nitride film 2 used in the gettering step can be used as a mask in the selective oxidation step for element isolation or the like. After the intrinsic gettering step is completed, the silicon nitride film 2 is used for selective oxidation. You may perform a process.

Further, although this intermediate heat treatment step is 700 ° C. as in the second embodiment, it is not limited to this value and may be in the range of 600 to 900 ° C. The range of 650 to 750 ° C. is more preferable, and by adopting this intermediate heat treatment step, dissociation of fine oxygen precipitates can be suppressed even if the temperature rising rate up to the subsequent third heat treatment step is increased. .

The third heat treatment step in this case is 1 hour, but it may be performed for 0 to 5 hours as in the case of the third embodiment. The longer the time, the greater the amount of oxygen precipitates deposited. Although the gettering effect is increased because the number of the elements increases, the processing time becomes longer and the productivity is reduced.

The temperature of this third heat treatment step is 110.
The temperature is not limited to 0 ° C., but may be in the range of 900 to 1350 ° C., more preferably in the range of 1000 to 1150 ° C., and the precipitation of oxygen precipitates may be reduced at low temperatures, while at high temperatures. After that, the precipitated oxygen precipitates are dissociated and reduced.

Also in the fourth embodiment, the time for the first heat treatment step can be saved by performing both the first heat treatment step and the well forming step, and the time for the second heat treatment step can be reduced. By shortening and increasing the temperature rising rate by adopting the intermediate heat treatment step, for example, in the case of FIG.
The processing time can be shortened as compared with 5 hours.

In the fourth embodiment, the temperature lowering rate and the temperature raising rate in the temperature lowering step and the temperature raising step are 4 to 4.
It is 6 ° C./min, but it is not limited to this value, and it may be 15 ° C./min or less in each case. If this speed is too low, the treatment takes too long, while if it is too high, oxygen precipitation occurs. Since a problem such as dissociation of nuclei occurs, for example, the temperature decreasing rate in steps 4 and 10 is 3 to
A range of 10 ° C./min is more preferable, and Step 6
And the temperature rising rate in step 8 is preferably 5 to 10 ° C./min. The first heat treatment step to the third heat treatment step and the intermediate heat treatment step in the fourth embodiment are all performed under normal pressure N ₂
It is done in an atmosphere.

In each of the above embodiments, a 500 Å thermal oxide film is provided on the surface of the silicon substrate 1. However, since this thermal oxide film suppresses the roughness of the surface of the silicon substrate 1, it has a thickness of 20 Å or more. It is good if there is a certain amount.

Further, although the thickness of the silicon nitride film 2 in each of the above embodiments is 1500 Å, it is not limited to this value, and the permeation of metal impurities and oxygen molecules is prevented and the permeation of oxygen atoms is allowed. The film thickness may be any suitable thickness, for example, a range of 1000 to 2000 Å is suitable.

Further, in the second and fourth embodiments provided with the intermediate heat treatment step, the temperature rising rates before and after the intermediate heat treatment step were both 5 ° C./min, but different from each other. The temperature rising rate may be adopted.

[0096]

According to the present invention, since the intrinsic gettering step is performed with the silicon nitride film 2 provided on the surface of the silicon substrate 1, it is possible to prevent metal impurities from invading from the outside with the high temperature heat treatment step. This can be prevented, and the heat treatment time at the initial stage of the process can be shortened by performing a part of the intrinsic gettering step and the heat treatment step associated with the well formation, thus improving the manufacturing yield and the manufacturing cost. It greatly contributes to the reduction.

[Brief description of drawings]

FIG. 1 is a time chart of the principle configuration of the present invention.

FIG. 2 is an explanatory diagram of an operation according to the present invention.

FIG. 3 is an explanatory diagram of a manufacturing process according to the first embodiment of this invention.

FIG. 4 is a time chart of the manufacturing process of the first embodiment of the present invention.

FIG. 5 is a time chart of the manufacturing process of the second embodiment of the present invention.

FIG. 6 is a time chart of the manufacturing process of the third embodiment of the present invention.

FIG. 7 is a time chart of the manufacturing process of the fourth embodiment of the present invention.

FIG. 8 is a time chart of a conventional intrinsic gettering process.

FIG. 9 is an explanatory diagram of a conventional intrinsic gettering process.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Nitride Film 3 Defect-Free Layer 4 Intrinsic Point Defect Generation Region 5 Oxygen Precipitation Nucleation Region 6 Oxygen Precipitation Precipitation Region 7 Mask 8 Well Region

Claims (10)

[Claims] 1. A step of depositing a silicon nitride film on a silicon substrate, a first heat treatment step of isothermally heat-treating the silicon substrate at 900 to 1350 ° C., and the silicon substrate 4
A second heat treatment step of isothermal heat treatment at 00 to 650 ° C., a third heat treatment step of isothermal heat treatment of the silicon substrate at 900 to 1350 ° C. for 0 to 5 hours, and a heat treatment of forming an impurity diffusion region in the silicon substrate. With the process
A method of manufacturing a semiconductor device, comprising performing at least part of the first to third heat treatment steps and a heat treatment step of forming an impurity diffusion region in the silicon substrate. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a silicon oxide film having a thickness of 20 Å or more is formed on the silicon substrate prior to the step of depositing the silicon nitride film. 3. The temperature lowering rate in the temperature lowering step between the first heat treating step and the second heat treating step is set to 15 ° C./minute or less, and between the second heat treating step and the third heat treating step. The temperature raising rate in the temperature raising step is set to 15 ° C./minute or less, and at least part of the third heat treatment step and the heat treatment step of forming an impurity diffusion region in the silicon substrate are performed together. Claim 1 or 2
The manufacturing method of the semiconductor device described in the above. 4. The method of manufacturing a semiconductor device according to claim 3, wherein at least one of the first heat treatment step and the second heat treatment step is performed for 30 minutes or more. 5. An intermediate heat treatment step of isothermally heat-treating the silicon substrate at 600 to 900 ° C. is provided between the second heat treatment step and the third heat treatment step, and the second heat treatment step and the intermediate heat treatment step are performed. 4. The semiconductor device according to claim 3, wherein the temperature rising rate between the heating step and the intermediate heating step and the heating step between the third heat processing step and the third heat processing step are 15 ° C./min or less. Production method. 6. The first heat treatment step, the second heat treatment step,
The method of manufacturing a semiconductor device according to claim 5, wherein at least one of the intermediate heat treatment steps is performed for 30 minutes or more. 7. A step of ion-implanting impurities into the silicon substrate is provided between the step of depositing a silicon nitride film on the silicon substrate and the first heat treatment step, and
The temperature lowering rate in the temperature lowering step between the first heat treating step and the second heat treating step is set to 15 ° C./min or less, and the temperature rising rate in the temperature raising step between the second heat treating step and the third heat treating step is increased. The temperature rate is set to 15 ° C./minute or less, and at least a part of the first heat treatment step and a heat treatment step of forming an impurity diffusion region in the silicon substrate are performed at the same time. A method for manufacturing a semiconductor device as described above. 8. The method of manufacturing a semiconductor device according to claim 7, wherein at least one of the isothermal heat treatments of the first heat treatment step and the second heat treatment step is performed for 30 minutes or more. 9. An intermediate heat treatment step of isothermally heat-treating the silicon substrate at 600 to 900 ° C. is provided between the second heat treatment step and the third heat treatment step, and the second heat treatment step and the intermediate heat treatment step are performed. 8. The semiconductor device according to claim 7, wherein the temperature raising rate in the temperature raising step between the first heat treatment step and the intermediate heat treatment step and in the temperature raising step between the third heat treatment step are 15 ° C./min or less. Production method. 10. The method of manufacturing a semiconductor device according to claim 9, wherein at least one of the first heat treatment step, the second heat treatment step, and the intermediate heat treatment step is performed for 30 minutes or more.