JP2707671B2 - Radiation detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation detection device.

2. Description of the Related Art Conventionally, a radiation detection apparatus using a dynamic read / write memory (DRAM) as a detection unit has been devised. FIG. 4 is a cross-sectional view showing a detection unit of a conventional radiation detection device. Reference numeral 1 denotes a semiconductor substrate made of silicon or the like, and the detection unit 10 includes a capacitance insulating film 11 and a capacitance electrode 21 made of polysilicon, which is also a source region of a switching transistor serving as a data writing unit. The data writing section includes a gate electrode 22, a gate insulating film 4, and a drain 23. 24 is a field oxide film and 25 is a channel stopper.

The range of α ray is 20-30um in silicon substrate (however,
The energy of α rays is about 5 MeV. ). Since the thickness of a silicon substrate used for manufacturing an LSI usually has a thickness of about 625 μm, only the α-ray incident from the surface of the silicon substrate needs to be considered. When α-rays pass through the surface of the device, electron-hole pairs are generated in a columnar shape with a radius of about 0.1 μm around the track of the α-rays. Since the energy required to generate one electron-hole pair is about 3.6 eV, when 9 MeV α-rays enter the silicon substrate, 2.5 × 10 ⁶ or more electrons
Hole pairs will be generated. Of the electron-hole pairs, the holes flow into the silicon substrate, but the electrons flow into the charge storage region (detection unit 10) formed by the semiconductor substrate 1 below the capacitive insulating film 11 due to diffusion or funneling. Come. Therefore, if “1” is written in the charge accumulation region, that is, if there is no electron, the state where electrons are accumulated, that is, “0” is written by the inflow of electrons. When the information of the memory cell is read in this state, 0 is read, which indicates that the storage information has been inverted from 1 to 0. Due to this soft error phenomenon, it can be detected that the α-rays have passed through the silicon substrate, particularly in the vicinity of the memory cell where 1 has become 0. In other words, 1 is written in all the memory cells at first, and then the reading is repeated after the memory cells are in a floating state. When 0 is read, it is determined that the α ray is incident. The α ray is actually detected during a period of several nsec. To several tens nsec. While the memory cell is in a floating state.
Since the line is incident on the silicon substrate, the time resolution is several tens of nanoseconds. Since the time of the floating state of the memory cell can be made long so that the information inversion due to the leak current does not occur, the time resolution can be changed from tens of nanoseconds to several milliseconds.

Radiation detectors that are inexpensive, compact, mechanically strong, and can be used in high-humidity environments and have excellent positional resolution and time resolution, such as those described above, are, for example, Nuclear Instruments and Methods (Nuclear Instruments
and Methodes) 169 (1980) 125-128.

However, the above-described conventional radiation detection device uses only the source region of the switching transistor, which is a data writing unit, as the radiation detection unit. There is a problem that the ratio is small and the intrinsic efficiency is small.

The present invention has been made in view of the above-described problems, and has a large proportion of the radiation detection area in the unit memory cell.
It is an object of the present invention to provide a radiation detection device with improved intrinsic efficiency.

Means for Solving the Problems To solve the above-mentioned problems, the present invention provides a data writing unit and a radiation detection unit formed on a semiconductor substrate, a data introduction unit that writes data to the detection unit, and a detection unit. Comparing the read data read and the data before writing to the detection unit from the data introduction unit, at least having an output read verification unit that outputs a signal when they do not match, the detection unit of the data writing unit It is provided with a configuration of being formed at the lower part.

According to the present invention, a radiation detection device having a large intrinsic efficiency can be realized by the above-described configuration, in which a region which has not conventionally contributed to radiation detection becomes a detection portion.

Embodiment (Embodiment 1) FIG. 1 is a block diagram of a radiation detecting apparatus according to an embodiment of the present invention. The known write data is written to the radiation detecting unit 26 by the data introducing unit 27, and after a predetermined time elapses, the data read and read unit 28 reads the read data read from the radiation detecting unit 26 and the write data before writing to the detecting unit 26. The comparison is performed by the read collation unit 28.
Data written by passing alpha rays from “1” to “0”
If the inversion has occurred, the comparison result between the read data and the write data does not match, and the data read collation unit 28 outputs a signal. The calculation display unit 29 counts the signals and displays the count value. Since the count value increases in proportion to the α-ray intensity, the α-ray intensity can be detected from the count value.

FIG. 2 is a sectional view showing a detection cell array having a radiation detector according to the first embodiment of the present invention. Reference numeral 1 denotes a P-type semiconductor substrate having an impurity concentration of about 10 ¹⁵ cm ³ , a detection unit 8 includes a capacitance insulating film 11 made of a silicon oxide film, and a plate electrode 12. A switching transistor serving as a data writing unit has a drain 2, a source 3, It comprises a gate insulating film 4 and a word line 5. The drain 2 is electrically connected to the bit line 6 via the contact window 7. The insulator 13 becomes an insulating separation region of the adjacent switching transistor. Since this separation method requires a smaller area than the LOCOS method, it is suitable for increasing the density of sensitive parts to radiation.

A voltage sufficient to invert the semiconductor substrate 1 sandwiching the insulating film 11 is always applied to the plate electrode 12. When α-rays enter while “1” is written, electrons induced by the α-rays due to diffusion and funneling flow into the inversion layer, causing a soft error phenomenon, and the α-rays are detected. . In the conventional structure, the radiation detection part is a depletion region immediately below the capacitance part insulating film. On the other hand, in the present embodiment, the radiation detection unit 8 is a depletion region immediately below the source 3 and a depletion region around the capacitive insulating film 11 below the element isolation region. The intrinsic efficiency increases significantly. Also, if BF ₂ or the like is deposited on the bit line 6 in FIG. 1, when α-rays are generated by the ¹⁰ B (n, α) ⁷ Li reaction when neutrons are incident, the neutrons It can be seen that the light has entered. ¹⁰ B (n,
The α) ⁷ Li reaction has a large cross section for thermal neutrons among neutrons. Therefore, the present invention is also an effective detector for thermal neutrons. Since neutrons alone do not cause a soft error phenomenon, if BF ₂ is not deposited, the detector will be only α-rays. Conversely, by depositing BF ₂ and then depositing a SiN film of about 40 μm or shielding it more easily with paper, alpha rays will not reach the Si substrate, and only neutron rays Become.

Embodiment 2 FIG. 3 is a sectional view showing a detection cell array having a radiation detection unit according to a second embodiment of the present invention. Reference numeral 1 denotes a p-type semiconductor substrate, a detection unit 9 includes an n ⁺ impurity diffusion layer 14, and a switching transistor includes a drain 2, a source 3, a gate insulating film 4, and a word line 5 as in the first embodiment. . The other numbers shown in FIG. 3 are the same as in the first embodiment, and will not be described here.

In the conventional example and the first embodiment, “0” and “1” can be written, but “1” writing is used as the radiation detection device. In this embodiment, only “1” can be written, and this is used. That is, only when the drain 2 is set at 3V (high voltage), the depletion layer between the source 3 and the impurity diffusion layer 14 and the substrate 1 spreads, and charges are accumulated. When α rays enter in this state, electrons induced by the α rays flow into the depletion layer due to the electric field and diffusion of the depletion layer, causing a soft error phenomenon, and the α rays are detected.

In this embodiment, the radiation detector 9 is a depletion region immediately below the source 3 and a depletion region around the impurity diffusion layer 14 below the element isolation region. It rises remarkably.

Advantageous Effects of the Invention As is clear from the above description, the present invention provides a radiation detecting section below a data writing section,
An area that has not contributed to the conventional radiation detection is also a detection portion, and has an effect of increasing the intrinsic efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a radiation detecting apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view showing a detecting cell array having a radiation detecting section according to the first embodiment of the present invention, and FIG. FIG. 4 is a sectional view showing a detection cell array having a radiation detecting section according to a second embodiment, and FIG. 4 is a sectional view showing a detecting section of a conventional radiation detecting apparatus. 2 ... Drain, 3 ... Source, 4 ... Gate insulating film,
5 word line, 6 bit line, 8, 9 detection section,
11 ... Capacitance insulation film thickness, 12 ... Plate electrode, 26 ... Radiation detector.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-40892 (JP, A) JP-A-63-61983 (JP, A) JP-A-63-124987 (JP, A) 29971 (JP, A)

Claims (3)

(57) [Claims] A data writing unit and a radiation detection unit formed on a semiconductor substrate; a data introduction unit for writing data to the detection unit; read data read from the detection unit; and a detection unit from the data introduction unit. A data read / comparison unit that compares the data before writing into the data write unit and outputs a signal when the data does not match, and the detection unit is formed below the data write unit. 2. The radiation detecting apparatus according to claim 1, wherein said radiation detecting section comprises a storage element using a capacitor. 3. A radiation detecting apparatus according to claim 1, wherein said radiation detecting section comprises an impurity diffusion layer having a conductivity type opposite to that of said semiconductor substrate.