TW202247484A - Single photon avalanche diode - Google Patents

Abstract

A single photon avalanche diode including a n-type semiconductor well layer, a p-type semiconductor well layer, and a side p-type-doping well layer is provided. The p-type semiconductor well layer is deposed on the n-type semiconductor well layer. The side p-type-doping well layer is deposed between the n-type semiconductor well layer and the p-type semiconductor well layer. The depth of the side p-type-doping well layer is less than the depth of the p-type semiconductor well layer. The p-type doping concentration of the side p-type-doping well layer is greater than the p-type doping concentration of the p-type semiconductor well layer.

Description

single photon collapse diode

The present invention relates to a photodiode, and in particular to a single photon avalanche diode (SPAD).

During the manufacturing process of semiconductor devices, impurity atoms are doped into the semiconductor to form P-type or N-type semiconductor regions. Among them, the ion implantation method (ion implantation) accelerates the ionized impurity atoms by an electric field, injects the impurity atoms into the semiconductor substrate, and diffuses the impurity atoms into the interior of the semiconductor substrate.

When a photon is irradiated on a single-photon collapse diode, the electrons separated from the hole enter the depletion region at the p-n junction, and the electrons are greatly accelerated by the electric field in the depletion region and hit other atoms , so that other atoms free more electrons to form a collapse current (avalanche current). The current value of the breakdown current is much larger than the original photocurrent, which can effectively improve the sensing sensitivity.

In the manufacturing process of single-photon collapse diodes, in order to create deep PN junctions to absorb more photons, multi-pass ion implantation is usually performed. The annealing process after ion implantation repairs the lattice defects generated during the ion implantation process by heating the silicon substrate, and allows the implanted impurity atoms to diffuse. If the heating time is not long enough, the implanted impurity atoms will not diffuse completely and evenly, and some regions with higher carrier concentration will be formed. In the P-type semiconductor region, these regions with higher carrier concentration will form an energy barrier for electrons, so that the photoelectrons generated on the surface can easily flow away from the side, and will not reach the collapse region (that is, the depletion region) to generate a collapse signal. This results in loss of photon detection probability (PDP).

The invention provides a single photon collapse diode, which can improve the photon detection rate.

In an embodiment of the present invention, the single photon breakdown diode includes an N-type semiconductor well layer, a P-type semiconductor well layer, and a P-type side doped layer. The P-type semiconductor well layer is configured on the N-type semiconductor well layer. The P-type side doped layer is disposed between the N-type semiconductor well layer and at least a part of the P-type semiconductor well layer. The depth of the P-type side doped layer is smaller than the depth of the P-type semiconductor well layer. The P-type doping concentration of the P-type side doping layer is greater than the P-type doping concentration of the P-type semiconductor well layer.

Based on the above, in the single photon collapse diode of the embodiment of the present invention, since the P-type side doped layer is arranged between the N-type semiconductor well layer and at least a part of the P-type semiconductor well layer, and the P-type side doped layer The P-type doping concentration of the layer is greater than the P-type doping concentration of the P-type semiconductor well layer, so it can prevent the photoelectrons formed in the P-type semiconductor well layer from entering the N-type semiconductor well layer through the side, so that the photoelectrons can effectively enter the PN junction The formed collapse region (that is, the strong electric field region) is accelerated, causing a collapse current and improving the photon detection rate.

1A is a schematic cross-sectional view of a single-photon breakdown diode according to an embodiment of the present invention, and FIG. 1B is a doping concentration distribution diagram of the single-photon breakdown diode of FIG. 1A . Please refer to FIG. 1A and FIG. 1B . In the figure, x is the position of the surface of the parallel single photon collapsing diode, and y is the depth position of the surface of the vertical single photon collapsing diode. The value in the upper left corner of FIG. 1B indicates the carrier concentration, and the unit is cm ⁻³ , where negative values represent P-type doping, and positive values represent N-type doping. The single photon breakdown diode 100 includes an N-type semiconductor well layer 110 , a P-type semiconductor well layer 120 and a P-type side doped layer 130 . The P-type semiconductor well layer 120 is disposed on the N-type semiconductor well layer 110 . The P-type side doped layer 130 is disposed inside the P-type semiconductor well layer 120 and is close to the N-type semiconductor well layer 110 . The depth d1 of the P-type side doped layer 130 is smaller than the depth d2 of the P-type semiconductor well layer 120 . In the embodiment shown in FIG. 1A and FIG. 1B , the depth d1 of the P-type side doped layer 130 is about 2.5 microns, and the depth d2 of the P-type semiconductor well layer 120 is about 3 microns. In addition, the P-type doping concentration of the P-type side doped layer 130 is greater than the P-type doping concentration of the P-type semiconductor well layer 120 .

In this embodiment, a PN junction J is formed between the P-type semiconductor well layer 120 and the N-type semiconductor well layer 110 , and the PN junction J forms a collapse region R. The P-type side doped layer 130 is disposed on a side near the N-type semiconductor well layer 110 above the PN junction J. In detail, in this embodiment, the N-type semiconductor well layer 110 includes a bottom 112 and sidewalls 114, the P-type semiconductor well layer 120 is disposed on the bottom 112, the sidewall 114 surrounds the P-type semiconductor well layer 120, and the P-type side is doped The layer 130 is disposed above the PN junction J close to the sidewall 114 and extends along the shape of the sidewall 114 .

In this embodiment, the P-type semiconductor well layer 120 has at least one high-concentration region 122, and the P-type doping concentration of the P-type semiconductor well layer 120 in at least one high-concentration region 122 is greater than that of the P-type semiconductor well layer 120 in at least one high-concentration region. For the P-type doping concentration near the concentration region 122 , the extension direction of at least one high-concentration region 122 is different from the extension direction of the P-type side doped layer 130 . When the photoelectrons formed in the P-type semiconductor well layer 120 move in the P-type semiconductor well layer 120 , the high-concentration region 122 will form a lateral energy barrier for the electrons, making the electrons more likely to move laterally. In this embodiment, because the P-type side doped layer 130 is arranged on the side of the side wall 114 of the N-type semiconductor well layer 110 above the PN junction J, it can form a vertical energy barrier for electrons, reducing the electrons passing through the side. The probability of entering the N-type semiconductor well layer 110 enables electrons to effectively enter the collapse region R formed by the PN junction J. The collapse region R has a strong electric field, so that the electrons are accelerated and hit other atoms, resulting in more The ionization of electrons causes a collapse current and increases the photon detection rate.

In this embodiment, the bottom of the P-type semiconductor well layer 120 and the bottom of the P-type side doped layer 130 are located at different levels. In this embodiment, the distance h between the bottom of the P-type semiconductor well layer 120 and the bottom of the P-type side doped layer 130 falls within a range of 0.5 microns to 2 microns. For example, the distance h between the bottom of the P-type semiconductor well layer 120 and the bottom of the P-type side doped layer 130 in FIG. 1A is about 0.5 μm. Because the P-type side doped layer 130 does not contact the PN junction J, photoelectrons can be prevented from triggering collapse at the place where the P-type side doped layer 130 contacts the PN junction J.

In this embodiment, the P-type doping concentration of the P-type semiconductor well layer 120 falls within the range of 10 ¹⁷ cm ^-3 to 5×10 ¹⁸ cm ^-3 , and the P-type doping concentration of the P-type side doping layer 130 The impurity concentration falls within the range of 10 ¹⁷ cm ^-3 to 5×10 ¹⁸ cm ^-3 . For example, in the embodiment of FIG. 1A , the P-type doping concentration of the P-type semiconductor well layer 120 is about 2×10 ¹⁷ cm ⁻³ , and the P-type doping concentration of the P-type side doping layer 130 is about 6 ×10 ¹⁷ cm ^-3 . In this embodiment, because the P-type doping concentration of the P-type side doped layer 130 is greater than the P-type doping concentration of the P-type semiconductor well layer 120, the P-type side doped layer 130 will affect the P-type semiconductor well layer 120. The photoelectrons in the photoelectrons form a higher energy barrier, preventing the photoelectrons from entering the N-type semiconductor well layer 110 through the sub-region of the P-type side doped layer 130 .

In the embodiment shown in FIG. 1A and FIG. 1B , the single photon breakdown diode 100 further includes a P-type heavily doped layer 140 and an N-type heavily doped layer 150 . The P-type heavily doped layer 140 is disposed on the P-type semiconductor well layer 120 . The N-type heavily doped layer 150 is disposed on the N-type semiconductor well layer 110 . In this embodiment, the P-type side doped layer 130 is disposed between the P-type heavily doped layer 140 and the N-type heavily doped layer 150 . In this embodiment, the P-type doping concentration of the P-type heavily doped layer 140 is greater than the P-type doping concentration of the P-type side doping layer 130, and the N-type doping concentration of the N-type heavily doped layer 150 is greater than N N-type doping concentration of the semiconductor well layer 110. In detail, in this embodiment, the N-type semiconductor well layer 110 includes a bottom 112 and sidewalls 114, the P-type semiconductor well layer 120 is disposed on the bottom 112, the sidewall 114 surrounds the P-type semiconductor well layer 120, and the N-type semiconductor well layer 120 is heavily doped. Layer 150 is disposed on top of sidewall 114 .

FIG. 2 is a diagram of the current density distribution of the single-photon collapse diode of FIG. 1A on the same section. Please refer to Figure 2. Likewise, x in the figure is the position parallel to the surface of the single photon collapsed diode, and y is the depth position perpendicular to the surface of the single photon collapsed diode. The value in the upper left corner of the figure is the indicated current density, and the unit is A‧cm ^-2 . As can be seen from the figure, in the P-type semiconductor well layer 120, the current density is low in the region near the interface of the P-type semiconductor well layer 120 and the sidewall 114 of the N-type semiconductor well layer 110; The region at the interface between 120 and the bottom 112 of the N-type semiconductor well layer 110 , that is, the region close to the collapse region R formed by the PN junction J, has a higher current density. This phenomenon means that the probability of photoelectrons moving to the side is small, and the probability of moving to the collapse region R below is relatively high. Therefore, the single-photon collapse diode 100 of this embodiment can effectively move photoelectrons to the collapse region R, thereby improving the photon detection rate.

FIG. 3 is a schematic cross-sectional view of a single-photon collapse diode of a comparative example. In the single photon breakdown diode 100' in Fig. 3, the P-type side doped layer 130 is not configured. FIG. 4 is a diagram of the current density distribution of the single-photon collapse diode in FIG. 3 on the same section. As can be seen from FIG. 4, in the P-type semiconductor well layer 120', between the high-concentration regions 122', the region near the interface of the P-type semiconductor well layer 120' and the side wall 114 of the N-type semiconductor well layer 110' , there is a channel with a higher current density, forming a lateral electron flow I; in the high-concentration region 122', on the path from the P-type heavily doped layer 140' to the collapse region R' formed by the PN junction J', There are regions of lower current density. This phenomenon is that the high-concentration region 122' distributed laterally in the P-type semiconductor well layer 120' forms an energy barrier to the photoelectrons moving in the P-type semiconductor well layer 120', which increases the probability of photoelectrons moving to the side. The moving photoelectrons cannot enter the collapse region R', thereby causing a collapse current, thus reducing the photon detection rate. In the single photon collapse diode of Figure 1A, the photon detection rate of the device is increased to 2.1%, while in the single photon collapse diode of Figure 3, the photon detection rate of the device is 1.4%.

FIG. 5 is a graph showing the relationship between the photon detection rate and the applied voltage of the single photon collapse diode of FIG. 1A and the single photon collapse diode of FIG. 3 . The data points in FIG. 5 reflect the effect of disposing the P-type side doped layer 130 in the single photon breakdown diode 100 on the photon detection rate PDP of the device. It can be seen from FIG. 5 that with the modulation of the applied voltage V _ex , the photon detection rate PDP (marked as a square data point in FIG. 5 ) of the single photon collapse diode 100 in FIG. 1A is always greater than that in FIG. The photon detection rate PDP of the single photon collapse diode 100 ′ of 3 (indicated as triangle data points in FIG. 5 ). It can be seen that, according to the embodiment of the present invention, disposing the P-type side doped layer 130 in the single photon collapse diode 100 element can effectively improve the photon detection rate of the element.

In this embodiment, the material of the N-type semiconductor well layer 110 is, for example, silicon doped with phosphorus, arsenic, antimony or a combination thereof. The material of the P-type semiconductor well layer 120 is, for example, silicon doped with boron, indium or a combination thereof. The material of the p-type side doped layer 130 is, for example, silicon doped with boron, indium or a combination thereof. The material of the P-type heavily doped layer 140 is, for example, silicon doped with boron, indium or a combination thereof. The material of the N-type heavily doped layer 150 is, for example, silicon doped with phosphorus, arsenic or a combination thereof. However, the present invention is not limited to the above materials.

To sum up, in the single photon breakdown diode of the embodiment of the present invention, since the P-type side doped layer is arranged on the side near the N-type semiconductor well layer above the PN junction, and the P-type side doped layer The P-type doping concentration of the P-type semiconductor well layer is greater than the P-type doping concentration of the P-type semiconductor well layer, so it can prevent the photoelectrons formed in the P-type semiconductor well layer from entering the N-type semiconductor well layer through the side, so that the photoelectrons can effectively enter the PN junction to form The collapse area of the photon is accelerated, causing a collapse current and increasing the photon detection rate.

100, 100': single photon collapse diode 110, 110': N-type semiconductor well layer 112: bottom 114, 114': sidewall 120, 120': P-type semiconductor well layer 122, 122': high concentration region 130: P-type side doped layer 140, 140': P-type heavily doped layer 150: N-type heavily doped layer d1, d2: depth h: spacing I: lateral electron flow J, J': PN junction R, R ': Crash zone V _ex : Applied voltage PDP: Photon detection rate x: Position y: Position

FIG. 1A is a schematic cross-sectional view of a single-photon collapse diode according to an embodiment of the invention. FIG. 1B is a graph of the doping concentration profile of the single photon collapse diode of FIG. 1A . FIG. 2 is a diagram of the current density distribution of the single-photon collapse diode of FIG. 1A on the same section. FIG. 3 is a schematic cross-sectional view of a single-photon collapse diode of a comparative example. FIG. 4 is a diagram of the current density distribution of the single-photon collapse diode in FIG. 3 on the same section. FIG. 5 is a graph showing the relationship between the photon detection rate and the applied voltage of the single photon collapse diode of FIG. 1A and the single photon collapse diode of FIG. 3 .

100: Single Photon Collapses Diodes

110: N-type semiconductor well layer

112: bottom

114: side wall

120: P-type semiconductor well layer

122: high concentration area

130: P-type side doped layer

140: P-type heavily doped layer

150: N-type heavily doped layer

d1, d2: depth

h: spacing

J:PN junction

R: crash zone

Claims (11)

A single photon collapse diode comprising: An N-type semiconductor well layer; A P-type semiconductor well layer configured on the N-type semiconductor well layer; and A P-type side doped layer is disposed inside the P-type semiconductor well layer and close to the N-type semiconductor well layer, the depth of the P-type side doped layer is smaller than the depth of the P-type semiconductor well layer, and the P-type semiconductor well layer is The P-type doping concentration of the side doped layer is greater than the P-type doping concentration of the P-type semiconductor well layer. The single photon collapse diode as claimed in item 1, wherein a PN junction is formed between the P-type semiconductor well layer and the N-type semiconductor well layer, and the PN junction forms a collapse region, and the P-type side The doped layer is disposed on the side of the N-type semiconductor well layer above the PN junction. The single-photon collapse diode as claimed in item 2, wherein the N-type semiconductor well layer comprises: a bottom, wherein the P-type semiconductor well layer is disposed on the bottom; and A side wall surrounds the P-type semiconductor well layer, and the P-type side doping layer is disposed above the PN junction close to the side wall and extends along the shape of the side wall. The single photon collapse diode as claimed in claim 1, wherein the bottom of the P-type semiconductor well layer and the bottom of the P-type side doped layer are located at different levels. The single photon collapse diode as claimed in claim 4, wherein the distance between the bottom of the P-type semiconductor well layer and the bottom of the P-type side doped layer is in the range of 0.5 microns to 2 microns. The single photon collapse diode as claimed in item 1, wherein the P-type doping concentration of the P-type semiconductor well layer falls within the range of 10 ¹⁷ cm ^-3 to 5×10 ¹⁸ cm ^-3 , and the P The P-type doping concentration of the type side doped layer falls within the range of 10 ¹⁷ cm ^-3 to 5×10 ¹⁸ cm ^-3 . The single-photon collapse diode as described in Claim 1 further includes: a P-type heavily doped layer disposed on the P-type semiconductor well layer; and An N-type heavily doped layer is arranged on the N-type semiconductor well layer. The single photon breakdown diode as claimed in claim 7, wherein the P-type side doped layer is disposed between the P-type heavily doped layer and the N-type heavily doped layer. The single photon breakdown diode as claimed in item 7, wherein the P-type doping concentration of the P-type heavily doped layer is greater than the P-type doping concentration of the P-type side doping layer. The single photon collapse diode as described in claim item 7, wherein the N-type semiconductor well layer comprises: a bottom, wherein the P-type semiconductor well layer is disposed on the bottom; and A side wall surrounds the P-type semiconductor well layer, and the N-type heavily doped layer is disposed on the top of the side wall. The single photon collapse diode as claimed in item 1, wherein the P-type semiconductor well layer has at least one high-concentration region, and the P-type doping concentration of the P-type semiconductor well layer in the at least one high-concentration region is greater than the P The P-type doping concentration of the semiconductor well layer near the at least one high-concentration region, the extension direction of the at least one high-concentration region is different from the extension direction of the P-type side doped layer.

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