JP2004221193A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device in which the increase of a switching speed is realized, inhibiting the rise of an on-state voltage, and its manufacturing method. <P>SOLUTION: A diode composed of an anode region 1, a cathode region 2 and a low-concentration region 3 formed between the anode region 1 and the cathode region 2, crystal defects are formed in a junction neighboring region of the anode region 1 and the low-concentration region 3 and in the cathode region 2. Both these crystal defects are formed by irradiating charged particles from the cathode region 2 side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device subjected to lifetime control and a method of manufacturing a semiconductor device including a lifetime control process.
[0002]
[Prior art]
The lifetime of semiconductor devices such as diodes, transistors, and thyristors is controlled as needed in order to increase the switching speed.
Lifetime control improves the switching speed by intentionally introducing an energy level, which is the recombination center, into the semiconductor region that composes the semiconductor device, and using this level to eliminate accumulated carriers by recombination. It is a technique to make it. Here, to generate recombination centers, a method of diffusing heavy metals such as Au and Pt has conventionally been the mainstream, but in recent years, methods of irradiating charged particles such as electrons, protons, and helium ions have become widespread. I have. In addition, while the lifetime control contributes to an increase in switching speed, the formation of a recombination center causes an increase in off-state leakage current. In addition, when the semiconductor device is in an on state, carriers are captured, which causes an increase in on-voltage (or on-resistance). Therefore, the lifetime control is generally performed under conditions that consider the balance between the switching speed, the leakage current, and the ON voltage.
[0003]
And, as the prior art, pn ^- in n ⁺ structure of the diode, p region and the n ^- junction region near the region, and the n ^- by performing lifetime control of the junction region near the n ⁺ region of the region It is known that the speed of turn-off is increased without deteriorating the characteristics at the time of conduction and the loss is reduced. (For example, Patent Document 1)
[0004]
[Patent Document 1]
JP-A-8-102545 (FIG. 1, paragraphs 0007 to 0009)
[0005]
[Problems to be solved by the invention]
However, the lifetime control described in Patent Document 1 is performed by double-sided irradiation of protons or double irradiation of protons and electron beams. Here, the double-sided irradiation of the proton includes a step of irradiating the proton through the anode surface of the diode and a step of irradiating the proton through the cathode surface. Therefore, the manufacturing process is troublesome. In addition, when protons are irradiated through the anode surface, a region near the surface is damaged, and the leakage current increases.
[0006]
Further, in the method described in Patent Document 1, since the lifetime control of the region near the junction of the n ⁻ region and the n ⁺ region is performed, carriers are captured in that region when the diode is turned on, and the anode is turned off. The on-voltage of the diode increases to increase the amount of hole injection from the diode.
[0007]
An object of the present invention is to simplify a method for manufacturing a semiconductor device including a lifetime control process. It is another object of the present invention to provide a semiconductor device which realizes a high switching speed while suppressing an increase in on-voltage, and a method of manufacturing the same.
[0008]
[Means for Solving the Problems]
The method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device having an anode region, a cathode region, and a low impurity concentration region formed between the anode region and the cathode region, And irradiating charged particles to a region near the junction between the anode region and the low impurity concentration region, and irradiating the cathode region with charged particles from the cathode region side.
[0009]
In this method, since both steps are performed by irradiating the charged particles from the cathode region side, both steps can be realized only by changing irradiation conditions. Further, since the charged particles are not irradiated from the anode region side, the anode region and the region near the surface of the low impurity concentration region are not damaged, and an increase in leakage current can be reduced.
[0010]
In the step of irradiating the cathode region with the charged particles, the charged particles may be irradiated to a region having an impurity concentration substantially equal to the impurity concentration near the surface of the anode region. When the diode is conducting, holes injected from the anode region reach a region in the cathode region having an impurity concentration substantially equal to that near the surface of the anode region. Therefore, if a recombination center is generated by irradiating the above-described region with charged particles, holes in the cathode region are efficiently eliminated when the diode is turned off, so that the switching speed can be increased. In addition, since the low impurity concentration region is not irradiated with the charged particles, an increase in on-voltage can be suppressed.
[0011]
Alternatively, ³ He may be irradiated as charged particles. According to this method, formation of a crystal defect in an unintended region can be suppressed, and a crystal defect can be accurately formed in a target region.
A semiconductor device according to the present invention is a semiconductor device having an anode region, a cathode region, and a low impurity concentration region formed between the anode region and the cathode region. Charged particles are irradiated to the region near the junction, and the charged particles are irradiated to a region in the cathode region where the impurity concentration is substantially equal to the impurity concentration near the surface of the anode region. As described above, it is possible to suppress an increase in the ON voltage and to increase the switching speed by this configuration.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating the structure of the semiconductor device according to the embodiment. Hereinafter, a diode will be described as an example of a semiconductor device according to the present invention.
[0013]
The diode according to the embodiment includes an anode region 1, a cathode region 2, and a low concentration region (low impurity concentration region) 3 formed between the anode region 1 and the cathode region 2. The anode region 1 is formed such that the concentration of the p-type impurity in the region near the surface is, for example, about 10 ¹⁶ / cm ³ . The cathode region 2 is formed such that the concentration of the n-type impurity in the region near the surface is, for example, about 10 ²⁰ / cm ³ , and the impurity concentration gradually decreases as the distance from the surface increases. ing. Further, n-type impurities are implanted into the low concentration region 3 at a low concentration.
[0014]
In the diode, a crystal defect as a recombination center for controlling the lifetime is formed in a region near the junction between the anode region 1 and the low-concentration region 3 and inside the cathode region 2. Here, each of these crystal defects is formed by irradiating charged particles so as to pass through the surface of the cathode region 2. Specifically, the step of irradiating the charged particles from the cathode region 2 side under conditions (irradiation energy or the like) such that the charged particles reach the region near the junction between the anode region 1 and the low-concentration region 3; Crystal defects are formed by the step of irradiating charged particles from the cathode region 2 side under conditions that reach a predetermined region in the region 2. At this time, the order of performing these two steps is not particularly limited. That is, any of the steps may be performed first. Further, these two steps can be performed by the same equipment because only the irradiation energy and the like are different.
[0015]
The charged particles to be irradiated are not particularly limited, but are, for example, protons, ³ He, and ⁴ He. However, since the distribution of protons is widened, it is difficult to concentrate crystal defects in a target region. In addition, ⁴ He has a short range and a region where a crystal defect can be formed is limited. Therefore, it is considered that ³ He is suitable as the charged particles to be irradiated.
[0016]
In the lifetime control by irradiation of charged particles, the charged particles are irradiated with irradiation energy corresponding to an area (depth) where a crystal defect as a recombination center is to be formed. In this case, only the target area is used. Instead, a recombination center is also formed in a peripheral region. However, the density of recombination centers formed by this irradiation locally increases in a target region. Therefore, in this specification, "irradiating a predetermined region with charged particles" refers to locally increasing the density of recombination centers in the predetermined region.
[0017]
As described above, in the diode according to the embodiment, crystal defects are formed in the region near the junction between the anode region 1 and the low-concentration region 3 and inside the cathode region 2. It is formed by irradiating charged particles from two sides. Therefore, the region near the junction on the surface of the low concentration region 3 of the anode region 1 is not damaged by the irradiation of the charged particles. Therefore, it is possible to suppress an increase in leakage current when the diode is off.
[0018]
When the charged particles are irradiated from the cathode region 2 side, crystals in a region near the surface of the cathode region 2 and the like are damaged, so that unnecessary crystal defects are formed there. However, in this region, the impurity concentration is extremely high (in the embodiment, about 10 ²⁰ / cm ³ ) and sufficient carriers exist, so that the on-resistance does not increase. That is, even if the charged particles are irradiated from the cathode region 2 side in the method of the embodiment, the on-voltage hardly increases.
[0019]
Further, in the diode of the embodiment, since crystal defects are formed in the region near the junction between the anode region 1 and the low-concentration region 3 and inside the cathode region 2, the switching speed can be increased while suppressing an increase in on-voltage. Can be achieved. That is, since crystal defects are formed in the region near the junction between the anode region 1 and the low-concentration region 3, the lifetime of carriers existing in the region near the pn junction is shortened, and the switching speed is increased. In the diode of the embodiment, unlike the semiconductor device described in Patent Document 1, no crystal defect is formed in the low-concentration region 3, so that the on-resistance of the region does not increase and the on-voltage increases. Will not be invited.
[0020]
By the way, when the diode of the embodiment is conducting (at the time of forward bias), carriers are injected from the high-concentration regions (the anode region 1 and the cathode region 2) at both ends into the low-concentration region 3, and the resistance of the region is very small. (Conductivity modulation). Then, along with this, holes injected from the anode region 1 pass through the low-concentration region 3 and are injected into the cathode region 2. At this time, the holes reach the region in the cathode region 2 where the impurity concentration is substantially the same as the impurity concentration in the region near the surface of the anode region 1. Therefore, in the diode of the embodiment, as shown in FIG. 1, a region in the cathode region 2 having an impurity concentration substantially equal to the impurity concentration near the surface of the anode region 1 is irradiated with charged particles. In addition, a crystal defect as a recombination center is formed. The lifetime of holes injected into the cathode region 2 is shortened by crystal defects formed in this region.
[0021]
Even if a crystal defect is formed in the cathode region 2, if the crystal defect is formed in a region having a lower impurity concentration than the vicinity of the surface of the anode region 1, the crystal defect is formed in the low concentration region 3. As in the case, the on-resistance increases. On the other hand, in the region where the impurity concentration is higher in the cathode region 2 than in the vicinity of the surface of the anode region 1, holes do not reach even when the diode is conducting, so that forming a crystal defect there is a reduction in carrier lifetime. Is not effective. Therefore, in the diode according to the embodiment, a limit region where holes injected from the anode region 1 reach (that is, a region in the cathode region 2 having an impurity concentration substantially equal to the impurity concentration near the surface of the anode region 1) A crystal defect is formed in the cathode region 2 so that holes existing in the cathode region 2 are efficiently eliminated when the diode is turned off.
[0022]
As described above, the diode of the embodiment does not irradiate the low-concentration region 3 with the charged particles, but charges the low-concentration region 3 with the charged particles in a region near the junction between the anode region 1 and the low-concentration region 3 and a predetermined region in the cathode region 2. By irradiating, both suppression of increase in on-voltage and increase in switching speed can be realized in a well-balanced manner.
[0023]
Incidentally, even if the inside of the cathode region 2 is not irradiated with charged particles, only the region near the pn junction (corresponding to the region near the junction between the anode region 1 and the low concentration region 3 in the embodiment) is irradiated with the charged particles. Thus, it is possible to achieve the same speed as the diode of the embodiment. However, in this case, the amount of crystal defects to be formed in the region near the pn junction needs to be increased, so that the forward voltage is significantly increased. Also, when high-speed switching is to be realized with this configuration, turn-off surge or ringing increases.
[0024]
In the above-described embodiment, a diode having a pn ⁻ n ⁺ configuration has been described. However, the present invention is not limited to this, and can be applied to a pin diode.
[0025]
【The invention's effect】
According to the present invention, since all the irradiation of the charged particles is performed from the cathode region side, the manufacturing process is simplified and the increase in the resistance of the anode region is avoided. In addition, since the charged particles are irradiated to the region near the junction between the anode region and the low impurity concentration region and the inside of the cathode region, it is possible to achieve both a suppression of an increase in on-voltage and an increase in switching speed in a well-balanced manner.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a structure of a semiconductor device according to an embodiment.
[Explanation of symbols]
1 Anode region 2 Cathode region 3 Low concentration region

Claims (4)

A method for manufacturing a semiconductor device having an anode region, a cathode region, and a low impurity concentration region formed between the anode region and the cathode region,
Irradiating charged particles to a region near the junction between the anode region and the low impurity concentration region from the cathode region side,
Irradiating the cathode region with charged particles from the cathode region side,
A method of manufacturing a semiconductor device having: It is a manufacturing method of Claim 1, Comprising:
In the step of irradiating the cathode region with charged particles, a region having an impurity concentration substantially equal to the impurity concentration near the surface of the anode region is irradiated with the charged particles. It is a manufacturing method of Claim 1 or 2, Comprising:
The charged particles are ³ He. An anode region, a cathode region, and a semiconductor device having a low impurity concentration region formed between the anode region and the cathode region,
Charged particles are irradiated to a region near the junction between the anode region and the low impurity concentration region,
A semiconductor device, wherein charged particles are irradiated to a region in the cathode region, the impurity concentration of which is substantially equal to the impurity concentration near the surface of the anode region.

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