JPS5813033B2 - semiconductor radiation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor detectors, and more particularly to the measurement of low energy nuclides of radiation and low noise semiconductor radiation detectors.

In recent years, surface barrier type semiconductor radiation detectors have been developed to measure energetic particles.

What is known as a typical surface barrier type semiconductor radiation detector is a detector in which a surface barrier is formed by vacuum-depositing a metal such as Au, Ti, or A7 onto a semiconductor crystal body such as Si, CaTe, or GaAs. There is.

This type of detector is constructed, for example, as shown in FIG.

In FIG. 1, a semiconductor wafer 1 is formed by molding an insulating material surrounding its outer periphery, has an annular mount 2 with a tapered inner periphery, and has an electrode layer 3 that forms a surface bond with the wafer. The electrode layers 4 that make ohmic contact are provided to cover the tapered surface of the mount base 2 and the peripheral edge thereof, respectively.

Further, in order to alleviate the edge effect of each electrode layer 3, 4, resins 5, 6 are filled and applied between the inner periphery of the mount base 2 and the electrode layer prior to adhesion of the electrode layer.

The detector shown in FIG. 1 configured in this way fills the fault between the mount 2 and the semiconductor wafer 1, and the synthetic resin coating layers 5 and 6 for preventing electric field misalignment are formed between the mount 2 and the wafer 1. If it is impossible to bury the wafer 1 on a gentle slope and the usage environment changes, such as in a place with significant temperature changes or in a place with severe mechanical vibration, A gap is created between the electrodes and the synthetic resins 5 and 6, making it impossible to obtain stable electrical contact, and the electrodes are often left open.

Furthermore, although it is possible to reduce the gap by selecting the synthetic resins 5 and 6 applied and reinforcing the conductive adhesive, on the other hand,
Both of these affect the surface of the wafer 1, causing problems such as channeling by the synthetic resin 5 and destruction of the electrode layer 3 that forms surface bonding, resulting in a significant deterioration of characteristics, resulting in a very low yield rate during manufacturing. There was a low drawback.

Furthermore, since the surfaces of the mount table 2, synthetic resin 5, and wafer 1 have many irregularities of various sizes, if it is necessary to reduce the thickness of the electrode layer 3 that forms the surface bond, the irregularities may prevent electrical contact. It is stable and has a high electrical resistance value.
This was causing noise in the detector.

Further, when it is desired to make the metal layer 3 forming the surface bond thinner, there is a drawback that the electrical contact becomes disconnected and the detector cannot function as a detector.

The present invention has been made in view of the above circumstances, and enables easy and stable contact between a metal layer forming a surface bond on a semiconductor wafer and a metal layer on a mounting table, and also reduces detector noise. Furthermore, the present invention provides a semiconductor radiation detector that can improve environmental resistance.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows one example of this, and is a sectional view of a surface barrier type detector.

Reference numeral 1 is a semiconductor wafer, for example, an n-type silicon wafer, and reference numeral 2 is an annular insulator mount having a tapered inner periphery, which is generally made of ceramic, acrylic, or the like.

This semiconductor wafer 1 is mounted on the annular tapered surface of a mounting table 2 with filling resins 5 and 6.

Reference numeral 3 denotes a metal layer forming a surface barrier, such as gold, which is deposited on the semiconductor wafer 1, the filling resin 5, and the mounting base 2 to a uniform thickness by, for example, vacuum deposition.

Reference numeral 4 denotes an electrode layer that makes ohmic contact, and aluminum, for example, is vacuum-deposited by the method described above.

On the surface of the semiconductor wafer 1 on which the surface barrier is formed, a metal layer 23, for example gold, is thickly vacuum-deposited from the center of the filling resin 5 to the mounting base 2, slightly from the center of the filling resin 5.

The electrode plates 7 and 8 are connected by pressure bonding to a metal layer forming a surface barrier and an ohmic contact metal layer on the mount table, respectively.

For example, in the structure of this embodiment, n
Using a Si crystal with a resistivity of 3000 Ω cm, a vacuum-deposited layer of gold with a thickness of 70 mm is applied to the metal layer 3 forming the surface barrier, and a vacuum-deposited layer 23 of 500 mm thick is applied to the outer periphery of this metal layer. Bias voltage of a surface barrier type radiation detector using nickel plate and aluminum for electrode plates 1 and 8, respectively, and a conventional radiation detector having a metal film thickness of 70 mm for the metal layer forming the surface barrier. Figure 3 shows the noise characteristics for

Both detectors have the same reverse current characteristics and capacitance characteristics.

Curve a in FIG. 3 is the characteristic of the above-described embodiment of the detector, and curve b is the characteristic of the conventional detector.

From this characteristic, it is clear that the noise of this embodiment is significantly lower than that of the conventional example.

This noise becomes a factor that reduces the measurement limit point and resolution in the case of radiation nuclide measurement and low energy measurement.

With the structure of the present invention, by using the same process multiple times without significantly changing the method of manufacturing the detector, more stable electrical contact can be obtained between the mount table and the wafer, and environmental resistance can be achieved. A dog detector can be easily produced.

Furthermore, since the noise value can be lowered, the sensitivity of the detector can be improved.

For example, when measuring low-energy radiation, the measurement could not be performed accurately because the energy of the radiation was lowered by the metal layer forming the surface bonding of the detector.

However, with the detector of the present invention, the metal layer that forms a direct surface bond to the wafer can be made extremely thin, for example, to a thickness of 20 mm, and the noise of the detector can be extremely low. It is very effective when measuring accurately and with a good signal-to-noise ratio.

This makes it possible, for example, to use a photometric detector as a highly sensitive detector with a large area and low energy loss.

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 4, the same parts as in FIG. 2 are given the same reference numerals.

A is a top half view seen from the top, and B is a sectional view.

An annular mounting table 2 having a tapered surface having a metallized layer 42 on both sides is used, and a metal layer 3 forming a surface barrier layer is uniformly deposited on the semiconductor wafer 1 by vacuum deposition.

A metal layer forming a surface barrier is deposited on this metal layer 3 in the shape of a slit or in various shapes from the portion forming the surface barrier layer on the wafer 1 to the metal metallized layer 42 on the mount table 2 .

On the other side of the semiconductor wafer 1, a metal 4 making ohmic contact is deposited up to the metallized layer of the mount 2.

The thickness of the ohmic contact metal layer 4 should be as thick as possible, but if you want to make this ohmic contact metal layer thinner, as described above, from the ohmic contact metal layer on the wafer 1 to the mounting base, form a ring. Alternatively, it is also possible to apply the ohmic contact metal layer in the form of a slit.

The electrodes are drawn out from the metallized layer 42 on the mount base 2 by soldering, welding, or the like.

This embodiment provides increased environmental resistance, allows for the production of a lower noise detector, and is also very effective in measuring incident radiation from ohmic contact metal layers with low energy loss.

As described above, according to the present invention, by gradually increasing the thickness of the metal layer forming the surface bond of the detector from the semiconductor wafer to the mount table, it is possible to easily draw out the electrodes on the surface forming the surface bond. In addition, stable electrical contact can be obtained against environmental changes, and the yield in manufacturing the detector can be improved.

Furthermore, since a lower noise characteristic is obtained than a detector having a surface bond of the same thickness, it is possible to measure low-energy radiation, and moreover, a detector that can be easily used as a photodetector with a large area and a low level can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional semiconductor radiation detector, and FIG. 2 is a sectional view of a semiconductor radiation detector according to an embodiment of the present invention.
FIG. 3 is a curve diagram showing noise characteristics of a conventional radiation detector and a radiation detector of the present invention, and FIG. 4 is a sectional view of another embodiment of the present invention. 1... Semiconductor wafer, 2... Mounting stand, 3...
Surface bond forming layer, 4... Ohmic contact layer, 5, 6...
Filled resin, 7, 8... Electrode plate, 23. 43... Surface bonding forming multiple metal layer, 42... Metallized layer, 47.
48... Electrode lead line.

Claims (1)

[Claims] 1. A semiconductor crystal body, a metal layer provided on one surface of the body and forming a surface bond with the body, a metal layer provided on the other surface of the body and in ohmic contact with the body, and a peripheral edge of the body In a surface barrier type semiconductor radiation detector comprising a supporting mounting base, the thickness of the metal layer forming the surface bonding is increased stepwise from the crystal body toward the mounting base, and the thick metal layer forming the surface bonding is increased stepwise from the crystal body to the mounting base. A semiconductor radiation detector characterized in that an electrode is drawn out from a layer portion.