JPH06103346B2 - Radiation detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation detection apparatus.

2. Description of the Related Art A radiation detection device using a dynamic read / write memory (DRAM) as its detection unit has been devised.

The advantage of using DRAM is that since data can be written in or read from a specific memory cell, it is possible to specify which memory cell the radiation has entered. That is, since the incident position of radiation can be specified and one data detector can be shared by many memory cells, integration is easy. FIG. 3 is a sectional view of the detecting portion of this device. Here, 1 is a semiconductor substrate made of silicon or the like, 4 is a gate insulating film, 11 is an insulating film of a capacitor portion, 31 is a dielectric film such as SiO ₂ , 60 is a protective film such as SiO ₂ doped with phosphorus, and 62 is Poly-Si as an electrode of the capacitor portion, 63 as poly-Si as a gate electrode, 64 as a field oxide film, 65 as an n ⁺ impurity diffusion layer as a channel stopper, and 67 as an n ⁺ impurity diffusion layer as a drain.

In this example, the semiconductor substrate 1 under the gate insulating film 4
The charge is accumulated in. Radiation in this charge storage region, especially α
When a line is incident, an electron-hole pair is generated on the semiconductor substrate 1, and electrons of this are collected in the charge storage region. Therefore, the original stored information is destroyed and erroneous information is stored. Then, the information in this memory cell is read and compared with the written information to determine whether the read information is correct information or erroneous information. Then, if wrong information is read, it can be detected that the radiation is incident there.

In this way, it is possible to realize a radiation detection apparatus that is inexpensive, compact, mechanically strong, can be used even in a high humidity environment, and has excellent position resolution and time resolution.

The above is for example Nuclear Instruments and Methodes 16
9 (1980) 125-128.

However, since the above-described conventional radiation detecting apparatus uses the planar structure capacitor (insulating film 11 in FIG. 3) as the detecting portion, the ratio of the radiation detecting region to the unit memory cell is small. It has the disadvantage of low intrinsic efficiency.

Means for Solving the Problems In order to solve the above problems, the present invention forms a capacitor, which is a memory element serving as a detection unit, by forming a groove in a semiconductor substrate or by stacking the capacitors, and in the conventional structure, The radiation detecting apparatus having a large intrinsic efficiency is realized by using a portion that cannot be the detecting portion as the detecting portion.

Effect According to the present invention, α is formed deep inside or above the semiconductor substrate.
It is possible to collect the electrons generated by the passage of lines and the like, and it is possible to realize a radiation detection apparatus having a large intrinsic efficiency.

Embodiment An embodiment of the present invention is shown in FIGS. 1 and 2. Figure 1 shows
FIG. 2 is a schematic view showing a plane configuration of a radiation detector array according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II ′ of FIG. For ease of explanation, the same components will be described with common numbers.

Here, 1 is a P-type semiconductor substrate having an impurity concentration of about 10 ¹⁵ cm ^-3 (impurity concentration is not limited to this), and 2 and 3 are arsenic ion implantations (for example, implantation energy 80 KeV, dose amount 6.0).
X 10 ¹⁵ cm ^-2 ) is an n ⁺ impurity diffusion layer formed as a drain and a source of the switching transistor, respectively. Reference numeral 4 is a gate insulating film having a thickness of 15 nm formed by oxidizing the semiconductor substrate 1, 5 is a word line made of poly-Si or poly-side, 6 is a bit line made of Al, etc. The bit line 6 is electrically connected through the contact window 7. Denoted at 10 is a depth of 3.0 μm and a width of 0.8 μ formed on the semiconductor substrate 1 by dry etching or the like.
In the groove of m, the storage electrode is finally formed inside the groove, and the insulating isolation region of the switching transistor is formed above the groove. The switching transistor is formed in the island region 20 surrounded by the groove 10. Reference numeral 11 is an insulating film formed on the side surface and the bottom surface inside the groove 10. Of these, the insulating film formed on the bottom surface is for separating adjacent cells from each other, and needs to be thicker than the insulating film on the side surface. Reference numeral 12 denotes a storage electrode, which is formed by depositing poly-Si etc. by chemical vapor deposition (CVD) and then by anisotropic dry etching etc.
It is formed by digging 0.8 μm from the shoulder part of the. A voltage sufficient to invert the portion of the semiconductor substrate 1 with the insulating film 11 on the side wall interposed is applied to the storage electrode 11 at all times.

Next, an insulator 30 such as SiO ₂ is embedded on the storage electrode 12 inside the groove to form an insulating isolation region of an adjacent switching transistor. This separation method is based on the conventional LOCOS
It requires less area than the law, and therefore
It is suitable for increasing the density of radiation sensitive parts. 31 is
It is an interlayer insulating film such as SiO ₂ and has a film thickness of 800 nm, but it is not limited to this.

The range of α rays is 20 to 30 μm in a silicon substrate (however,
The energy of α rays is about 5 MeV). The thickness of a silicon substrate, which is used in the manufacture of LSI, is usually 625μ.
Since there is a thickness of about m, only α rays incident from the surface of the silicon substrate will be considered. When α-rays are transmitted from the surface of the device, electron-hole pairs are generated around the track of α-rays in a cylindrical shape with a radius of about 0.1 μm. The energy required to generate a pair of electron-hole pairs is about 3.6 eV, so when a 9 MeV α-ray enters a silicon substrate, 2.5 × 10 ⁶
Hole pairs will be generated. Of the electron-hole pairs, holes flow into the silicon substrate, but electrons flow into the charge storage region by the diffusion or funneling phenomenon. Therefore, if 1 is originally written in the charge storage region, that is, if there is no electron, the flow of electrons causes a state where electrons are stored and a state where 0 is written. Here, when the information in the memory cell is read, 0 is read out, and it can be seen that the stored information is inverted from 1 to 0. This phenomenon is called a soft error. As a result, it can be detected that the α ray has passed through the silicon substrate, particularly near the memory cell in which 1 becomes 0. In other words, it is determined that the α ray is incident when 0 is read while 1 is first written in all the memory cells and then the reading is repeated after the floating state of the memory cells. The α-ray is actually detected when the memory cell is in a floating state and when the α-ray is incident on the silicon substrate between several nsec. And several 10 nsec. Has a time resolution of several tens of nanoseconds. Since the floating time of the memory cell can be extended to the extent that information inversion due to leakage current does not occur, the time resolution can be changed from several tens of nanoseconds to several milliseconds.

If BF ₂ etc. is deposited on the bit line 6 in FIG. 2, α rays are emitted by the ¹⁰ B (n, α) ⁷ Li reaction when neutrons are incident, and the above mechanism causes , Α
It can be seen that the line was generated, that is, the neutron was incident. ^{The 10} B (n, α) ⁷ Li reaction has a large reaction 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 the soft error phenomenon, if BF ₂ is not deposited, it will be a detector for α rays only. On the contrary, by depositing BF ₂ and then depositing a SiN film of about 40 μm, or by shielding it with paper most easily,
The rays will not reach the Si substrate, and the detector will be a neutron ray only detector.

Next, the reason why the detection efficiency of the present embodiment is higher than that of the conventional radiation detection apparatus will be described. In the conventional structure, the radiation detecting portion is the insulating film (1 in FIG. 3) of the capacitance portion.
1) Only the depletion region directly below. Therefore, the area occupies a small portion of the unit cell, and among the electrons generated by the α rays passing through the silicon substrate, the one actually collected in the capacitance portion is within the total range of 20 to 30 μm. , Only a few microns on the surface of the silicon substrate. On the other hand, in this embodiment, the radiation detection portion is the source (3 in FIG. 2).
The depletion region directly below and the depletion region on the silicon substrate side of the capacitive insulating film (11 in FIG. 2), which is integrated and has a groove, has a large proportion in the unit cell. Since about half of the electrons generated by the α-rays are collected, the sensitivity (specific efficiency) of the radiation detection apparatus is significantly increased.

Further, these effects can also be obtained by stacking and forming the capacitor section on the semiconductor substrate.

EFFECTS OF THE INVENTION As described above, according to the present invention, by forming a capacitor by laminating on the inner sidewall of a groove formed in a semiconductor substrate or above the substrate, it has not conventionally contributed to detection. There is an effect that electrons generated by the transmission of α rays can be collected in a deep portion of the semiconductor substrate and the intrinsic efficiency is increased.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a memory cell of a detector of a radiation detecting apparatus according to an embodiment of the present invention, and FIG. 2 is a line I- of FIG.
FIG. 3 is a schematic sectional view showing a conventional radiation detecting device. 1 ... semiconductor substrate, 2 ... drain, 3 ... source, 4
... gate insulating film, 5 ... word line, 6 ... bit line,
7 ... Contact window, 10 ... Groove, 11 ... Insulating film, 12 ...
Storage electrode, 30 Insulator, 31 Interlayer insulation film, 32
Isolation insulation film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sueki Baba 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference US Patent 4140909 (US, A)

Claims (2)

[Claims] 1. A plurality of detecting sections using capacitors formed on a semiconductor substrate as storage elements, a data writing section for writing data in the storage elements, read data read from the detecting sections, and the detection. A data read collating unit that compares the data before writing to a unit and outputs an error signal when the comparison result does not match; an addressing unit that specifies whether to write or read the specific storage element data; Radiation characterized in that a capacitor as a storage element is formed in a groove formed in the semiconductor substrate, including a counting display section for counting error signals and displaying an address of the storage element which has output the error signal. Detection device. 2. A radiation detecting apparatus according to claim 1, wherein a capacitor as a memory element is formed on a side wall of a groove formed on the semiconductor substrate.