JPS6390140A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a desired N-type region of high resistivity for a device by a method wherein, after a P-type substrate whose resistivity is more than 1000OMEGA.cm and whose oxygen concentration is 2 X 10<17>m 1 X 10<18>/cm<3> has been heat-treated at over 650 deg.C which is necessary for the production process of a semiconductor device,the substrate is heat-treated at 400-500 deg.C. CONSTITUTION:If an N-type region of high resistivity, which is necessary for a Schottky barrier or a PN junction, is to be formed on a prescribed semiconductor device after the prescribed semiconductor device has been manufactured by means of a P-type Si substrate which was processed by a Czochralski method, the following procedure is used. That is to say, if a semiconductor device having a Schottky barrier or a PN junction is to be manufactured by means of an Si wafer processed by a Czochralski method, the semiconductor device is first manufactured by an ordinary method wherein a P-type wafer whose resistivity is more than 1000A.cm and whose oxygen concentration is 2 X 10<17>m1 X 10<18>/cm<3> is heattreated at over 650 deg.C. After that, the wafer is heat-treated at 400-500 deg.C, and a desired N-type region of high resistivity is obtained by making use of contained oxygen as a donor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, such as a radiation detection device, a photodetection device, a high voltage semiconductor device, etc., especially a semiconductor device having an n-type high resistivity region. involved.

[Summary of the invention]

The present invention is to manufacture a target semiconductor device using a p-type substrate having a specific resistance of 1000Ω·0111 or more and an oxygen concentration of 2×1017 to I×10” cm−3.
If this manufacturing process involves heat treatment at 650°C or higher, heat treatment at 400°C to 500°C is performed after this heat treatment step to form an n-type high resistivity region in the original p-type substrate. The oxygen concentration contained in the substrate is converted into a thermal donor, the p-type impurity in the p-type substrate is canceled out by this donor, and the substrate is converted into an n-type substrate with high resistivity, which can be used for radiation detection devices, photodetection devices, and high voltage resistance. To stably form a high resistivity n-type region required for semiconductor devices and the like.

[Conventional technology]

For example, in semiconductor devices such as radiation detection devices, photodetection devices, and high voltage semiconductor devices, an n-type high resistivity silicon substrate is used, and a Schottky barrier or a pn junction is formed thereon to produce the desired semiconductor device. will be held.

The method for manufacturing this type of silicon semiconductor substrate is as follows:
For example, a method has been adopted in which a silicon substrate is cut out from a crystal grown by the floating zone method (FZ method). However, recently, there has been a demand for the growth of large-diameter silicon substrates and, along with this, large-diameter silicon crystals, especially for the purpose of improving performance and reducing costs in the above-mentioned semiconductor devices and the like. However, with the FZ method, it is difficult to produce crystals with a diameter of 150 mm or more, and furthermore, as the diameter increases, the amount of impurities incorporated increases, making it difficult to obtain crystals with high resistivity. There are problems in terms of price, yield, quality, etc.
This tends to hinder the development and popularization of the various semiconductor devices mentioned above. In addition, since the crystal obtained by the FZ method has a low oxygen content of less than I When the above-mentioned various semiconductor devices are formed using this method, there are problems such as deterioration of characteristics. These problems become more pronounced as the diameter of the grown crystal increases, and this point also hinders the development and popularization of the above-mentioned semiconductor devices.

On the other hand, when crystal growth is performed by the Chickralski method (CZ method), a large amount of oxygen is generally taken in from the crucible containing the raw material melt used for this, and the oxygen concentration in the grown crystal is, for example, IX 10"cm"3 or more, the concentration of thermal donors generated by this oxygen becomes too high, or there are many electrically active impurities such as boron B that are mixed in from the crucible during crystal growth. Therefore, there is a problem that it is difficult to stably and reliably obtain the desired high resistivity crystal.

In contrast, the so-called MCZ method, in which crystal growth is performed by the CZ method under the application of a magnetic field, is capable of growing crystals with a large diameter, and is also disclosed in, for example, Japanese Patent Publication No. 58-50951. By applying a magnetic field to the conductive crystal growth raw material melt, the apparent viscosity due to the magnetohydrodynamic effect is increased and the convection of the melt is reduced. The oxygen concentration in the grown crystal can be sufficiently visualized, and if necessary, the oxygen concentration in the grown crystal can be increased by, for example, selecting the relative rotation speed between the pulled crystal and the raw material melt. The concentration can be reliably controlled and selected over a wide range.

However, in either case, if the rIJ elementary concentration is too low, a problem will occur with crystallinity, and if it is high, there will be a problem of inhibiting the increase in specific resistance due to the generation of thermal donors. However, since the generation rate of thermal donors is affected by the heat treatment during the manufacturing process of the semiconductor device, it is difficult to obtain a semiconductor device with stable characteristics.

[Problem that the invention seeks to solve]

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

[Means for solving problems]

The present invention provides a method for manufacturing a semiconductor device having at least an n-type high resistivity region, in which the resistivity is 1000 Ω·cm or more and the oxygen concentration is 2 x 1017 to I x 10110 l.
A 8' p-type substrate (hereinafter referred to as a starting substrate) is prepared, and a Schottky barrier, a pn junction, and an electrode are formed on it to manufacture the desired semiconductor device. Especially in the manufacturing process, 65
If a heat treatment process of 650°C or higher is involved, such as a thermal diffusion process of 0°C or higher, the process is repeated after completing this process.
Heat treatment is performed at 00°C to 500°C to convert the oxygen concentration in the p-type substrate into a thermal donor. The p-type impurity in the substrate is canceled out by the thermal donor, and the thermal donor converts it into an n-type with high specific resistance. Then, an n-type high resistivity region is formed in at least a part of the substrate, and a target semiconductor device is manufactured.

The p-type full substrate in the manufacturing method of the present invention can be cut out from a p-type crystal obtained by the MCZ method, and the MCZ method allows accurate control of the oxygen concentration as described above. can be done.

[Effect]

According to the above-mentioned manufacturing method of the present invention, the concentration of the entire p-type substrate is reduced to 2.
X 10110l7" or more, that is, by setting the oxygen concentration in the crystal grown by, for example, the MCZ method to obtain this p-type substrate to 2x10110l7' or more, thermal stress and the generation of crystal defects can be effectively reduced Although it is possible to suppress the
By using a type substrate, thermal donors generated by oxygen cancel out the acceptors and invert the conductivity type to n-type with high resistivity, so the oxygen concentration in the substrate is relatively high at 2 x 1017 cta-" or more. concentration,
Therefore, target semiconductor devices such as radiation detection devices, photodetection devices, and high voltage semiconductor devices having excellent crystallinity and stable characteristics can be manufactured.

In addition, in the present invention, heat treatment at 400 to 500 degrees Celsius is performed after the process involving heat treatment at 650 degrees Celsius or higher is completed, so it is possible to ensure the presence of a thermal donor in the end and ensure the n-type high temperature. A resistivity region can be formed. That is, it has been confirmed that the thermal donor disappears by heat treatment at 650°C or higher, but in the present invention, after the heat treatment at 650°C or higher, the thermal donor is
By performing the heat treatment at .degree. C., it is possible to reliably generate thermal donors, and it is possible to form a semiconductor region with a desired high resistivity, for example, 5000 Ω·cm.

〔Example〕

A p-type silicon single crystal of 1500 Ωcm is prepared by the MCZ method, a silicon semiconductor substrate is cut out from this, and a Schottky barrier is formed by plating or vapor-depositing a Schottky metal, and an electrode, for example, is formed on the surface of the silicon semiconductor substrate. A radiation detection device was fabricated by depositing gold (Au), and finally the substrate was heat-treated at 450°C to form an n-type 5000Ω
・cm, and as a result, a radiation detection device was manufactured in which a Schottky barrier was formed on an n-type substrate with a specific resistance of 5000 Ω・cm.

In this case, the starting substrate, i.e. the initial p-type 1500Ω
・The acceptor concentration in the silicon substrate of clI+ is approximately 9 X 1012c+++-', and the donor concentration in the n-type region of 5000 Ω cm, which is finally converted to n-type, is approximately 8 X 10''cm-'. , in this case donor concentration equal to acceptor concentration and 50
Since the donor concentration corresponding to 00 Ω・cIll is supplied by a thermal donor using oxygen, the thermal donor is 9 X 10"(cm-"
) + 8x10” (cm-3) = 9.8X 1
011012(') would be sufficient.

On the other hand, Figure 1 shows the measurement results of the relationship between the oxygen concentration in the crystal and the thermal donor concentration when heat-treated at 450°C.
) were subjected to this heat treatment for 1 hour, 16 hours and 100 hours, respectively.
Showing the results over time. According to this figure 1, 450°
In the case of heat treatment of C, the above-mentioned 9,8X 10'2c
To obtain a thermal donor of m-3, initially 7.5X 1
In the case of oxygen concentration of 0110l7', heat treatment for 1 hour from curve (1), and in the case of 5,4X 1017cm-3, heat treatment for 16 hours from curve (2), and 3,5
In the case of 10"cm-', 100 hours of heat treatment will generate 9.8X 10" cm-3 of thermal donors, forming the above-mentioned n-type region with high resistivity of 5000 Ωcm. Become.

As the oxygen concentration increases, the amount of thermal donors generated increases, so in order to obtain a predetermined amount of thermal donors, the heat treatment time must be shortened, but if the heat treatment time is too short, the amount of thermal donors generated will be controlled. becomes difficult. However, it is possible to select a certain amount of time, for example, by increasing the heat treatment temperature, e.g.
If the temperature is set to 00°C, the generation rate of thermal donors will be reduced to a fraction of that at 450°C, so the heat treatment time can be increased accordingly.

From these facts, the starting substrate, that is, rlif in the crystal
It has been confirmed that the fi concentration is desirably less than I x 10''cm-'.

Furthermore, Fig. 2 shows the heat treatment time and oxygen concentration necessary to generate the aforementioned 9.8 x 1012 cm''3 thermal donor, and the horizontal axis is shown as the square root of time t. According to this measurement result, Oxygen concentration is 1×10” cm−
3 (and the required heat treatment time will be shorter, but 4)
By selecting the temperature of the heat treatment at 50°C, that is, annealing, at around 400°C or close to 500°C, as will be explained later, to slow down the generation rate of thermal donors, oxygen up to IX 10" cm-3 can be achieved. It was confirmed that it is possible to form an n-type region with high resistivity even if the concentration is increased.

Figure 3 shows the occurrence of thermal donors that has already been reported. In other words, curve (31) has an oxygen concentration of 16X.
(32) is a p-type Si crystal obtained by the CZ method with an oxygen concentration of 4 x 10110l7', and (32) is a p-type Si crystal obtained by the MCZ method with an oxygen concentration of 4 x 10110l7'.
This shows the measurement results of resistivity versus heat treatment time when heat treated (4th International Symposium on Silicon Materials Science).
and Technology (Fourth Internat)
ional Symposium on Sil'1c
on MaterialsScience and T
technology ) May 1981 pp90-100
reference). According to this, the oxygen concentration is 16X 1017cm
``3, even if a p-type crystal with a low resistivity (approximately 10 Ω・cll) is heat-treated at 450°C, it will be converted to an n-type crystal in about 1 hour, but the oxygen concentration is 4 x 10'' cm-
In case 3, the p-type crystal with low resistivity of 13Ω/Cl remains p-type even after heat treatment for more than 200 hours, and no change in resistivity is observed.With this high oxygen concentration, thermal donor Although it is possible to convert a p-type to an n-type due to the large number of occurrences, it is difficult to convert a resistivity of 10 Ω·ca into an n-type with a high resistivity of several thousand Ω·CI. The acceptor concentration of p-type 1oΩ・C1l resistivity is approximately 1.4X 10”c+g-3, and to cancel this and make it n-type with 5000Ω・cm, 1.4X
1015 (cs-3) + 8 x 10” (cn
+-3) thermal donor is required. However, since the amount of 8 X 10" cm-3 to be controlled is only 0.06% of the total thermal donor, it can hardly be controlled. In contrast, in the above-mentioned example ((
8XIO”) / (9×1017 + 8 X 10
”) ) X 100 = 8.2%, making it easy to control.

Furthermore, in the case of a p-type resistivity of 1 oΩ·Cff1, the change in resistivity itself within the substrate is only a few percent, making control even more difficult. Therefore, in order to obtain an n-type substrate with high resistivity by utilizing the generation of thermal donors, it is desirable to use a p-type crystal with high resistivity, and the crystal growth is performed using MC.
It has been confirmed that in the case of a structure made of Z, a resistance of 1000 Ω·C11 or more is desirable in consideration of practical limits and the like.

〔Effect of the invention〕

As mentioned above, according to the production method of the present invention, active
Ni rI! The occurrence of thermal stress can be suppressed by preparing a substrate containing a predetermined amount of oxygen, that is, by performing crystal growth, and by activating this oxygen as a thermal donor, this substantially cancels out the acceptors contained in the substrate. Furthermore, since the target n-type substrate is converted to an n-type substrate with a high specific resistance, it is possible to use a large-diameter substrate by applying crystal growth using MCZ, and the crystal defect density can be reduced by reducing thermal stress. This combination of low resistivity and the ability to reliably form an n-type region with low resistivity results in high sensitivity and stable characteristics that can be used in, for example, radiation detection devices or photodetection devices, resulting in improved yields and Therefore, it is possible to reduce costs.

[Brief explanation of the drawing]

Figure 1 is a curve diagram showing the amount of thermal donor generated by heat treatment at 450°C, Figure 2 is a curve diagram showing the amount of thermal donor generated by heat treatment at 450°C.
A curve diagram showing the measurement results of the relationship between the time required to generate a thermal donor of 10110 l2" and the oxygen concentration. Figure 3 is a curve diagram showing the relationship between the heat treatment time at 450°C and the resistivity with each oxygen concentration. be.

Claims (1)

[Claims] In a method for manufacturing a semiconductor device having at least an n-type high resistivity region, the resistivity is 1000 Ωcm or more and the oxygen concentration is 2 x 10^1^7 to 1 x 10^1^8 cm^-^3.
65 in the manufacturing process of the semiconductor device on the p-type substrate of
400℃ ~ after completing the process involving heat treatment at 0℃ or higher
A method for manufacturing a semiconductor device, comprising performing heat treatment at 500° C. to form the n-type high resistivity region.