CN101409086B - Antimony-bismuth phase-change alloy mask read-only super-resolution disc - Google Patents

Abstract

An antimony-bismuth phase-change alloy mask read-only super-resolution optical disc, the structure of which includes a dielectric layer, a mask layer and a disc base, wherein the dielectric layer is composed of silicon nitride; the mask layer is composed of an antimony-bismuth alloy, namely, a SbxBi(1-x) thin film, wherein the x value varies in the range of 0.7 to 0.9. The antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention has the characteristics of simple structure, low readout power, high sensitivity and good readout cyclicity.

Description

Antimony-bismuth phase-change alloy mask read-only super-resolution disc

technical field

The invention belongs to the field of optical storage of information technology, and is a read-only super-resolution optical disc of an antimony-bismuth phase-change alloy mask. Compared with the currently used mask materials, the antimony-bismuth intersecting alloy mask read-only super-resolution optical disk of the present invention has the characteristics of simple structure, low readout power, high sensitivity, good readout cycle, etc., and has important applications prospect.

Background technique

With the development of high-density optical storage technology, the information recording point is getting smaller and smaller, which is much smaller than the diffraction limit of the optical head. In the field of optical storage, the improvement of storage density largely depends on the readout technology of information. When the recorded information points are very small, and a readout laser spot contains two or more recording points, the information will not be distinguished and read out. Super-resolution readout technology may be an important development direction of next-generation optical storage technology, and has very important application value and significance. Yasuda et al. used germanium antimony tellurium (GeSbTe) film as a mask to realize super-resolution reading of read-only optical discs first, see Yasuda K, Ono M, Aratani K, FukumotoA and Kaneko M 1993 Jpn.J.Appl.Phys.325210 . Mask materials play an important role in super-resolution techniques. Then antimony (Sb), silver indium antimony tellurium (AgInSbTe) and platinum oxide (PtO _x ) were used as mask materials, see Wei J S, Ruan H, Shi H R and GanF X 2002 Chin.Sci.Bull.47 1604; Zhang F, Wang Y, Xu W D and Gan F X2005 Opt. Eng. 445. However, since super-resolution optical discs have more layers and more complex structures than ordinary optical discs, the required recording and reading powers are very high. The read-out power of the read-only super-resolution optical disc constituted by the above mask is greater than 3mW, far greater than the read-out power of 0.5mW of the common read-only optical disc. High readout power produces high heat accumulation, which leads to the diffusion of atoms in the film layer, the destruction of information recording points, the reduction of the number of readout cycles, and greatly reduces the service life of the optical disc. It is particularly important to find a mask material with low readout power.

Contents of the invention

The problem to be solved by the present invention is to overcome the above-mentioned technical defects of the read-only super-resolution optical disc caused by the excessively high readout power, and to propose a read-only super-resolution optical disc with an antimony-bismuth phase change alloy mask, The optical disc should have simple structure, low readout power, high sensitivity and good readout cycle.

Technical solution of the present invention is as follows:

A kind of antimony-bismuth phase-change alloy mask read-only super-resolution optical disc, its structure includes a medium layer, a mask layer and a disc base, characterized in that the medium layer is made of silicon nitride; the mask layer is made of The antimony-bismuth alloy is composed of SbxBi(1-x) thin film, where the value of x varies from 0.7 to 0.9.

The thickness of the mask layer 02 is 30-90 nm. This mask layer 02 is used for the super-resolved readout of spots smaller than the diffraction limit.

The thickness of the dielectric layer 01 is 20-100 nm. The dielectric layer 01 is used to improve the stability of the mask layer 02 and prevent its oxidation.

Technical effect of the present invention:

Compared with prior art, experiment shows: antimony-bismuth phase-change alloy mask read-only super-resolution optical disk of the present invention, on the dynamic testing device that laser wavelength (λ) is 780nm, numerical aperture (NA) is 0.45 (this device The spot diameter is 1.22λ/NA≈2100nm) and the recorded spot at 380nm is read out. Moreover, compared with the read-only super-resolution optical disc of the previous mask material, it has a lower readout power of 0.5mW while realizing super-resolution readout, which is 100% of the read-out power of the current ordinary read-only optical disc. Same. However, the read-out power of the read-only super-resolution optical disc of the currently used mask material is generally greater than 3mW, for example, both Sb and AgInSbTe are 4mW. High readout power will generate high heat accumulation, resulting in the diffusion of atoms in the film layer, the destruction of information recording points, the reduction of the number of readout cycles, and ultimately reduce the service life of the optical disc. The antimony-bismuth phase-change alloy mask read-only super-resolution disc of the present invention solves this technical problem well. This is because the antimony-bismuth alloy film is a material with a high contrast between solid state and molten state. During the rotation of the optical disc, due to the high overlap temperature between the light spots at the front of the light spot, a molten state region is formed when the melting point exceeds the melting point. The cooler rear of the point is the solid state. Since the reflectivity of the melting state of the antimony-bismuth film is lower than that of the solid state, only the information at the back of the light point is reflected to the receiver, and the information of the melting state in front of the light point is masked, so the light point is effectively reduced. Small achieves the role of super-resolution. The antimony bismuth film here functions both as a mask layer and as a reflection layer. And because the melting point of the antimony-bismuth alloy film is relatively low, about 325°C, super-resolution readout can be realized only with a low readout power.

The antimony-bismuth phase-change alloy mask read-only super-resolution optical disk of the invention has the characteristics of simple structure, low readout power, high sensitivity, good readout cycle, etc., and has important application prospects.

Description of drawings

Fig. 1 is a structural diagram of an antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention.

Fig. 2 is the disc base of the antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention.

Fig. 3 is a diagram of a dynamic testing device used in the present invention.

Fig. 4 is the relationship between the reading signal-to-noise ratio and the reading power of the embodiment of the antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention.

Fig. 5 shows the relationship between the read signal-to-noise ratio and the thickness of the mask layer in the embodiment of the antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

Please refer to FIG. 1 first. FIG. 1 is a structural diagram of an antimony-bismuth phase-change alloy mask read-only super-resolution optical disc according to the present invention. It can be seen from the figure that the antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention has a structure comprising a dielectric layer 01, a mask layer 02 and a disc base 03, and the dielectric layer 01 is made of silicon nitride; The mask layer 02 is made of antimony-bismuth alloy, that is, SbxBi(1-x) film, where the value of x varies from 0.7 to 0.9.

The thickness of the mask layer 02 is 30-90 nm. This mask layer 02 is used for the super-resolved readout of spots smaller than the diffraction limit.

The thickness of the dielectric layer 01 is 20-100 nm. The dielectric layer 01 is used to improve the stability of the mask layer 02 and prevent its oxidation.

Pit points with a diameter of 380 nm are prefabricated on the polycarbonate disk substrate 03 with a thickness of 1.2 mm as information points, as shown in Figure 2. The preparation process of the antimony-bismuth phase-change alloy mask read-only super-resolution optical disk is as follows: using the method of magnetron sputtering (the sputtering pressure is 7.0×10 ^-4 Pa), on the disk base 03 as shown in Figure 2 Sequential sputtering: alloy mask layer 02 and dielectric layer 01, wherein the dielectric layer 01 is silicon nitride with a thickness of 30nm, and the alloy mask layer 02 is an antimony-bismuth alloy SbxBi(1-x) with a thickness of 10-170nm, where the value of x For 0.7, 0.8 and 0.9, multiple discs were produced.

The dynamic readout device is shown in Fig. 3, the semiconductor laser 1 has a wavelength (λ) of 780nm and a numerical aperture (NA) of 0.45. The laser beam passes through the polarizer 2 and the polarizing beam splitter 4 , and irradiates the optical disc 8 driven by the motor 9 through the mirror 6 . When the light beam hits the information point, it is reflected by the mirror 6, the polarizing beam splitter 4 and 5 in the form of reflected light, and passes through the polarizer 3 to transmit the change of reflectivity to the information receiver 10. Calculated according to the optical disc dynamic readout diffraction limit formula λ/(4NA), it is 433nm, which exceeds the recording spot diameter of 380nm in Figure 2, and the traditional read-only optical disc with aluminum as the reflective layer cannot get any signal. However, the antimony-bismuth mask read-only optical disc of the present invention can read higher signals. The read signal-to-noise ratio was optimized by comparing seven groups of mask layers with different thicknesses in the range of 10-170nm with an x value of 0.9, as shown in Figure 5, it was found that the optimal thickness of the mask layer was 30-90nm. The antimony-bismuth phase-change alloy mask read-only super-resolution disc of the present invention not only realizes super-resolution readout but also significantly reduces readout power. As shown in Figure 4, when the read power is 0.5mW, the maximum signal-to-noise ratio is obtained, and the signal-to-noise ratio is kept stable with the increase of power, reaching the same read-out power as the current common read-only optical disc. This is mainly because the antimony-bismuth alloy film has a lower melting point (~325°C) compared with the current mask materials (the melting point of Sb film is higher than 600°C, and that of AgInSbTe is 482°C). In addition, the signal-to-noise ratio of the antimony-bismuth phase-change alloy mask read-only super-resolution optical disk of the present invention does not change substantially after more than 4500 cycles of reading. The antimony-bismuth alloy masks with x values of 0.7 and 0.8 have similar super-resolution readout effects to the antimony-bismuth alloy masks with x of 0.9, and the number of readout cycles is more than 4000 and 4300 times, respectively. The specific results are shown in Table 1 . For the antimony-bismuth alloy SbxBi(1-x), when the x value is higher than 0.9, the melting point of the alloy film is higher, resulting in an increase in the readout power; and when the value is less than 0.7, with the increase of bismuth in the alloy film, the mask Decreased stability, resulting in reduced readout cycle times for super-resolution discs. Considering comprehensively, the optimal range of x value is between 0.7-0.9. The dielectric layer silicon nitride acts as a protective mask. For alloy masks with x values of 0.7, 0.8 and 0.9, its optimum thickness range is also 20-100nm, see Table 1. It can be seen that the antimony-bismuth phase-change alloy mask read-only super-resolution optical disc of the present invention can realize super-resolution readout at lower power, avoid disc substrate deformation caused by high readout power, and record points damage and reduction in disc life.

In summary, the antimony-bismuth phase-change alloy mask read-only super-resolution optical disk of the present invention has good super-resolution readout performance; it has much lower readout power than the read-only optical disk of the current mask material, almost Same as ordinary read-only optical discs; information readout is stable and the number of readout cycles is high. Therefore, it has an important application prospect in the field of optical storage.

Table 1

X value The best thickness range Minimum read power Read the number of cycles Optimum dielectric layer thickness 0.9 30-90nm 0.5mW ≥4500 20-100nm 0.8 30-100nm 0.5mW ≥4300 20-100nm 0.7 25-110nm 0.5mW ≥4000 20-100nm

Claims (3)

1. a kind of antimony-bismuth phase-change alloy mask read-only super-resolution optical disk, its structure comprises medium layer (01), mask layer (02) and disc base (03), it is characterized in that described medium layer (01 ) is made of silicon nitride; the mask layer (02) is made of antimony-bismuth alloy, that is, Sb _x Bi _1-x thin film, wherein the value of x varies from 0.7 to 0.9. 2. The antimony-bismuth alloy mask read-only super-resolution optical disc according to claim 1, characterized in that the thickness of the mask layer (02) is 30-90 nm. 3. The antimony-bismuth alloy mask read-only super-resolution optical disc according to claim 1, characterized in that the thickness of the medium layer (01) is 20-100 nm.

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