JPH0810694B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, for example, a radiation detecting device, a photodetecting device, a high breakdown voltage semiconductor device, etc., particularly a semiconductor device having an n-type high resistivity region. Involved in.

[Outline of Invention]

The present invention has a specific resistance of 1000 Ω · cm or more and an oxygen concentration of 2 × 10 5.
^When manufacturing a target semiconductor device on a p-type substrate of ¹⁷ to 1 × 10 ¹⁸ cm ^-3 , if this manufacturing process involves heat treatment at 650 ° C. or higher, after this heat treatment process is completed, 40
The oxygen concentration contained in the original p-type substrate is converted into a thermal donor by performing heat treatment at 0 ° C. to 500 ° C. to form an n-type high resistivity region, and the p-type in the p-type substrate is converted by this donor. Impurities are canceled out and converted into an n-type substrate having a high specific resistance to stably form an n-type region having a high specific resistance required for a radiation detecting device, a photodetecting device, a high breakdown voltage semiconductor device and the like. To do.

[Conventional technology]

For example, in a semiconductor device such as a radiation detection device, a photodetection device, or a high breakdown voltage semiconductor device, an n-type high resistivity silicon substrate is used, and a Schottky barrier or a pn junction is formed on the substrate to fabricate a target semiconductor device. Is done.

As a method for producing this kind of silicon semiconductor substrate, for example, a method of cutting out a silicon substrate from a crystal body grown by a floating zone method (FZ method) is adopted. However, recently, there has been a demand for growing a large-diameter silicon substrate, and accordingly, a large-diameter silicon crystal body for the purpose of improving the performance and reducing the cost particularly in the above-described semiconductor device. However, in the FZ method, the diameter
There is a problem that it is difficult to produce a crystal with a diameter of 150 mm or more, and as the diameter increases, it becomes difficult to obtain a crystal with a high specific resistance due to a large amount of impurities being taken in. There is a problem in terms of quality and the like, which tends to hinder the development and spread of the above-mentioned various semiconductor devices. The crystals obtained by the FZ method have an oxygen content of 1
Since the concentration is as low as × 10 ¹⁷ cm ^-3 or less, the crystal is vulnerable to thermal stress and crystal defects are more likely to occur, and when various semiconductor devices described above are formed using a silicon substrate cut out from this, characteristics There are problems such as deterioration. These problems become more prominent as the diameter of the grown crystal becomes larger, which also impedes the development and spread of the above-mentioned semiconductor device.

On the other hand, when a crystal is grown by the Czochralski method (CZ method), generally, the uptake of oxygen from the crucible in which the raw material melt used for this is stored is large, and the oxygen concentration in the grown crystal is, for example, 1 or less. × 10 ¹⁸ cm ^-3 or more is also Oyobi, Toka concentration of thermal donors is too high caused by oxygen, for example electrically active impurities such as boron B is often introduced by incorporating such from similarly crucible during the crystal growth Therefore, there is a problem that it is difficult to obtain a desired high resistivity crystal in a stable and reliable manner.

On the other hand, in the so-called MCZ method of growing a crystal by the CZ method under the application of a magnetic field, it is possible to grow a crystal having a large diameter, and for example, there is a disclosure thereof in Japanese Patent Publication No. 58-50951. As described above, by applying a magnetic field to the crystal-growing raw material melt having conductivity, the apparent viscosity due to the magnetic fluid effect is increased and the convection of the melt is reduced, so that the crystallinity is improved and, for example, the oxygen concentration is increased. The oxygen concentration in the grown crystal can be increased by, for example, selecting the relative rotational speed between the pulled crystal and the raw material melt crucible, if necessary. It is possible to make reliable control selections across the board.

However, in any case, when the oxygen concentration is too low, there is a problem in crystallinity, and when the oxygen concentration is high, there is a problem of inhibition of high specific resistance due to generation of a thermal donor. Since the generation rate of thermal donors is affected by the heat treatment in the manufacturing process of the semiconductor device, there is a problem that it is difficult to obtain a semiconductor device having stable characteristics.

[Problems to be solved by the invention]

The present invention can solve the above-mentioned problems,
The present invention provides a method for manufacturing a semiconductor device that can reliably manufacture a semiconductor device having an n-type high resistivity region.

[Means for solving problems]

The present invention relates to a method of manufacturing a semiconductor device having at least an n-type high resistivity region, which is a p-type substrate having a resistivity of 1000 Ω · cm or more and an oxygen concentration of 2 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ^−3. (Hereinafter, this is referred to as a starting substrate) is prepared, and for example, a Schottky barrier or a pn junction, and further, an electrode is formed to manufacture a desired semiconductor device. When a heat treatment step of 650 ° C or higher is involved, such as a heat diffusion step of ℃ ° C or higher, after finishing this step, heat treatment at 400 ° C to 500 ° C is performed again to reduce the oxygen concentration in the p-type substrate described above. The purpose is to cancel p-type impurities in the substrate that has been made into a thermal donor by a thermal donor and then convert it into an n-type having a high specific resistance to form an n-type high specific resistance region in at least a part of the substrate. To manufacture a semiconductor device You.

The p-type starting substrate in the manufacturing method of the present invention can be used by being cut out from the p-type crystal body obtained by the MCZ method. According to the MCZ method, the oxygen concentration can be accurately controlled as described above. It can be carried out.

[Action]

According to the above-described manufacturing method of the present invention, the concentration of the p-type starting substrate is set to 2
By selecting at least 10 ¹⁷ cm ^-3 or more, that is, by setting the oxygen concentration in the crystal grown by the MCZ method for obtaining this p-type substrate to at least 2 × 10 ¹⁷ cm ^-3 , thermal stress and therefore crystal defects are caused. In spite of being able to effectively suppress the occurrence of
By using the high resistivity p-type substrate as described above, the acceptor is canceled by the thermal donor generated by oxygen and the conductivity type is inverted to the high resistivity n-type, so that the oxygen concentration in the substrate is 2 ×. A relatively high concentration of 10 ¹⁷ cm ⁻³ or more, and therefore excellent in crystallinity, a semiconductor device intended to have stable and excellent characteristics, for example, a radiation detection device,
It is possible to manufacture a photodetector and a high breakdown voltage semiconductor device.

Further, in the present invention, since the step involving heat treatment at 650 ° C. or higher is finished and the heat treatment at 400 ° C. to 500 ° C. is subsequently performed, it is possible to make sure that the thermal donor is finally present and to make sure the n-type high temperature. A specific resistance region can be formed. That is, the thermal donor was confirmed to disappear by heat treatment at 650 ° C. or higher, but in the present invention, a step of performing heat treatment at 400 ° C. to 500 ° C. was performed after the heat treatment at 650 ° C. or higher. The thermal donor can be reliably generated by the high specific resistance, for example, 5000Ω ・ cm.
It is possible to form a semiconductor region having a high specific resistance.

〔Example〕

A p-type 1500 Ω · cm silicon single crystal is prepared by the MCZ method, a silicon semiconductor substrate cut out from this is prepared, and a Schottky barrier is formed by plating or vapor depositing a Schottky metal on this surface, and an electrode such as Gold Au
To produce a radiation detector, and finally
A heat treatment was carried out at a temperature of ° C to convert the substrate into an n-type 5000 Ω · cm, and as a result, a radiation detecting device was produced in which a Schottky barrier was formed on the n-type substrate having a specific resistance of 5000 Ω · cm.

In this case, the starting substrate, that is, the initial p-type 1500Ω
Acceptor concentration on a silicon substrate of cm is almost 9 × 10
The donor concentration is ¹² cm ⁻³ , and the donor concentration in the n-type region of 5000 Ω · cm finally converted to the n-type is about 8 × 10 ¹¹ cm ⁻³ . That is, in this case, since the donor concentration equal to the acceptor concentration and the donor concentration corresponding to 5000 Ω · cm are supplied by the thermal donor of oxygen, the thermal donor is 9 × 10 ¹² (cm ⁻³ ) + 8 × 10 5. ¹¹
(Cm ^-3 ) = 9.8 × 10 ¹² (cm ^-3 ).

On the other hand, FIG. 1 shows the measurement results of the relationship between the oxygen concentration in the crystal and the thermal donor concentration when heat treatment was performed at 450 ° C. (1), (2) and (3) in FIG. The results of performing this heat treatment for 1 hour, 16 hours and 100 hours respectively are shown. According to FIG. 1, in the case of heat treatment at 450 ° C., in order to obtain the above-mentioned thermal donor of 9.8 × 10 ¹² cm ^-3 , the curve (1) was initially used in the case of an oxygen concentration of 7.5 × 10 ¹⁷ cm ^-3. Heat treatment for 1 hour, and for 5.4 × 10 ¹⁷ cm ^-3 , curve (2) for 16 hours, 3.5 × 10 ¹⁷ c
In the case of m ^-3 , it will be 9.8 × 10 ¹⁸ cm ^-3 if heat treated for 100 hours.
Thermal donors are generated, and the n-type region having a high specific resistance of 5000 Ω · cm is formed.

Then, as the oxygen concentration increases, the amount of thermal donors generated increases, so the heat treatment time must be shortened to obtain a predetermined amount of thermal donors, but if the heat treatment time is too short, the amount of thermal donors generated can be controlled. Becomes difficult. However, it is possible to select a certain time, for example, by increasing the heat treatment temperature for that purpose, for example,
If the temperature is 400 ° C., the generation rate of the thermal donor is reduced to a fraction of that in the case of 450 ° C. Therefore, the heat treatment time can be lengthened accordingly.

From these facts, it was confirmed that the oxygen concentration in the starting substrate, that is, the crystal was desired to be 1 × 10 ¹⁸ cm ⁻³ or less.

Further, FIG. 2 shows the heat treatment time and oxygen concentration necessary for the generation of the above-mentioned thermal donor of 9.8 × 10 ¹² cm ⁻³ , and the horizontal axis is shown as the square root of the time t. According to this measurement result, when the oxygen concentration approaches 1 × 10 ¹⁸ cm ^-3 , the required heat treatment time becomes shorter, but the heat treatment at 450 ° C, that is, the annealing temperature is about 400 ° C or as will be described later. 1x10 by selecting a temperature near 500 ° C and slowing the generation rate of thermal donors
It was confirmed that an n-type region with high resistivity can be formed even if the oxygen concentration is increased to ¹⁸ cm ^-3 .

Figure 3 shows the generation status of thermal donors that have already been reported. That is, the curve (31) has an oxygen concentration of 16 × 10
^The p-type Si crystal obtained by the CZ method of ¹⁷ cm ^-3 , (32) is the p-type Si crystal obtained by the MCZ method of 4 × 10 ¹⁷ cm ^-3 of oxygen concentration when heat-treated at 450 ° C., respectively. It shows the measurement results of the resistivity with respect to the heat treatment time (4th International Symposium on Silicon Materials Science and Technology (Fourth Inter
national Symposium on Silicon Materials Science an
d Technology) 1981, May pp90-100). According to this, when the oxygen concentration is 16 × 10 ¹⁷ cm ^-3 , the specific resistance is low and about 10 Ω ・
Even if a p-type crystal of cm is heat-treated at 450 ° C, it will be converted to n-type by heat treatment for about 1 hour, but the oxygen concentration is 4 × 10 ¹⁷ cm.
^In the case of ^-3 , the p-type crystal having a low specific resistance of 13 Ω · cm remains p-type even after the heat treatment for 200 hours or more, and no change in the specific resistance is observed. When the oxygen concentration is high as described above, thermal donors are often generated and the p-type can be converted to the n-type, but the one having a specific resistance of 10 Ω · cm has a high specific resistance of several thousand Ω · cm. It is difficult to mold. It is p
Type 10 Ω · cm resistivity acceptor concentration is about 1.4 × 10 ¹⁵ cm ^-3
And to cancel this out and make it an n-type of 500 Ω · cm
1.4 × 10 ¹⁵ (cm ^-3 ) + 8 × 10 ¹¹ (cm ^-3 ) thermal donor is required. However, since 8 × 10 ¹¹ cm ⁻³ to be controlled is only 0.06% as compared with the whole thermal donor, the control is hardly possible. On the other hand, in the above-mentioned embodiment, {(8 × 10 ¹¹ ) / (9 × 10 ¹² + 8 × 10 ¹¹ )} ×
Since 100 = 8.2%, its control is easy.

Further, when the p-type specific resistance is 10 Ω · cm, the change in the specific resistance itself within the substrate is also a few%, so that it becomes more difficult to control. From this, in order to obtain an n-type substrate having a high specific resistance by utilizing the generation of a thermal donor, it is desirable to manufacture it by a p-type crystal having a high specific resistance, and it is practical when crystal growth is constituted by MCZ. 1000 considering the limits
We confirmed that Ω · cm or more is desirable.

〔The invention's effect〕

As described above, according to the production method of the present invention, it is possible to suppress the occurrence of thermal stress by preparing a substrate containing a predetermined amount of oxygen in advance, that is, performing crystal growth, and activate this oxygen as a thermal donor. By substantially canceling out the acceptor contained in the substrate and turning it into an n-type to obtain an n-type substrate having a desired high resistivity, for example, by applying crystal growth by the MCZ method, a large-diameter substrate can be formed. It is applicable to, for example, a radiation detection device or a photodetection device because it can be used, the crystal defect density is reduced due to the reduction of thermal stress, and an n-type region having a low specific resistance can be reliably formed. With high sensitivity and stable characteristics, it is possible to improve the yield and thus reduce the cost.

[Brief description of drawings]

Fig. 1 is a curve diagram showing the amount of thermal donors generated by heat treatment at 450 ℃, and Fig. 2 is the relationship between the oxygen concentration and the time required to generate 9.8 × 10 ¹² cm ^-3 thermal donors at 450 ℃ heat treatment. And FIG. 3 is a curve diagram showing the relationship between heat treatment time at 450 ° C. and each oxygen concentration of resistivity.

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device having at least an n-type high specific resistance region, wherein the specific resistance is 1000 Ω · cm or more and the oxygen concentration is 2 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ p. The n-type high resistivity region is formed on the mold substrate by finishing the process involving the heat treatment at 650 ° C. or higher in the semiconductor device manufacturing process and then performing the heat treatment at 400 ° C. to 500 ° C. Manufacturing method of semiconductor device.