JP4864317B2 - LIGHT EMITTING DEVICE TESTING APPARATUS AND LIGHT DETECTING ELEMENT FOR LIGHT EMITTING ELEMENT TESTING APPARATUS - Google Patents

Description

  The present invention relates to a light emitting element testing apparatus and a light detection element for a light emitting element testing apparatus.

Conventionally, as a test apparatus for performing a characteristic evaluation test of a high-power semiconductor laser element, an apparatus in which a light detection element is provided on the emission surface side of the semiconductor laser element and the light output of the semiconductor laser element is measured by the light detection element is known. Yes. The apparatus of Patent Document 1 is one of such test apparatuses, and a dimming optical filter is inserted between the semiconductor laser element and the light detection element as a countermeasure against output saturation of the light detection element.
Japanese Patent Laid-Open No. 10-19663

  In the above-described test apparatus, an installation space for the optical filter is required, so that the apparatus becomes large.

  When the optical filter is inserted so as to be perpendicular to the optical axis of the light emitted from the semiconductor laser element, the emitted light is reflected by the surface of the optical filter, and the reflected light returns to the semiconductor laser element. As a result, the operation of the semiconductor laser element becomes unstable, causing a problem that the characteristic evaluation test cannot be performed with high accuracy.

  On the other hand, when the optical filter is inserted so as to be inclined with respect to the optical axis of the light emitted from the semiconductor laser element, there is a possibility that the reflected light generated by the emitted light returns to the semiconductor laser element. Reduced. However, if the test apparatus has a plurality of pairs of semiconductor laser elements and photodetecting elements arranged in parallel, the reflected light generated by one semiconductor laser element may return to the adjacent semiconductor laser element. As a result, there still arises a problem that the characteristic evaluation test cannot be accurately performed.

  Therefore, an object of the present invention is to provide a light-emitting element test apparatus and a light-detecting element for a light-emitting element test apparatus that can accurately perform a characteristic evaluation test and can be downsized.

A light-emitting element testing apparatus according to the present invention includes a light-detecting element that receives monitor light emitted from a light-emitting element and outputs a photocurrent, and the characteristics of the light-emitting element based on a drive current or a photocurrent to the light-emitting element. A light-emitting element test apparatus for performing an evaluation test, comprising: a thermostatic chamber that houses the light- emitting element and a plurality of the light-detecting elements disposed opposite to the light- emitting element, and a light-absorbing layer on a light incident surface of the light-detecting element The light absorption layer has a plurality of micro holes for receiving a part of the monitor light at the light incident surface, and the area and the number of each of the plurality of micro holes depend on the light emitting element. When the emission amount of the monitor light is 5 × 10 ⁻² W or less, the photocurrent is set so as not to be saturated, and the aperture ratio defined by the total area of the plurality of micropores is 1 to 30 %, And the light detecting element is A first conductivity type substrate; a second conductivity type impurity region formed on a portion of the upper surface of the substrate; and an insulating film formed on the impurity region. The light absorbing layer is formed by applying a material of the light absorption layer on the insulating film or by a sputtering method.

  According to the light emitting element test apparatus of the present invention, since the light absorbing layer having the fine holes is provided on the light incident surface of the detecting element, the monitor light emitted from the light emitting element enters the light absorbing layer. The monitor light that has entered the portion of the light absorption layer other than the fine holes is absorbed by the light absorption layer, and the monitor light that has entered the fine holes reaches the light incident surface of the light detection element. Generation of reflected light can be reduced by the light absorption layer.

  Even when the monitor light is reflected on the light incident surface, the wall surface of the fine hole is a light absorbing layer, and thus the reflected light is absorbed by the inner wall surface of the fine hole. As described above, the generation of reflected light is suppressed, and even when the reflected light is generated, the possibility that the reflected light returns to the light emitting element is reduced. Therefore, it is possible to accurately perform the characteristic evaluation test of the light emitting element. .

  In addition, by providing a light-absorbing layer with fine holes on the light incident surface of the light detection element, the monitor light is shielded and only a part of the monitor light is input to the light detection element, thereby reducing the photocurrent and detecting light. The optical filter (ND filter) required to extend the saturation of the element to a higher incident power can be omitted. In this case, the installation space for the optical filter is not required, and the size can be reduced. In addition, the optical filter adjusts the light attenuation rate depending on its thickness, so that it requires strict manufacturing. On the other hand, the light absorption layer has a light attenuation rate depending on the number and size of fine holes (holes). Can be adjusted. Further, since this processing is performed by photolithography, it can be performed with high precision and no variation.

  When the light emitting element is visible or near infrared light, the light absorbing layer preferably contains a black resin. When black resin is used as the material of the light absorption layer, it is possible to absorb light components in the visible light region and the near infrared region among the components of the monitor light. Therefore, generation | occurrence | production of reflected light can be suppressed more reliably.

  In the case of an ultraviolet light emitting element, the material of the light absorption layer is preferably polysilicon. When polysilicon is used as the material of the light absorption layer, there is no deterioration due to ultraviolet rays, and it is possible to absorb the ultraviolet light component of the monitor light components. Note that polysilicon is applicable to an ultraviolet light-emitting element because it has a property of passing light having a wavelength longer than visible.

The polysilicon of the light absorption layer is preferably provided with an antireflection film. By forming the antireflection film on the polysilicon, the generation of reflected light can be more reliably suppressed. The antireflection film includes a first antireflection film and a second antireflection film provided on the upper and lower surfaces of the light absorption layer, respectively.

As described above, the photodetecting element includes the first conductivity type substrate, the second conductivity type impurity region formed on a part of the upper surface of the substrate, and the insulating film formed on the impurity region. The light absorption layer is formed on the insulating film . By providing the insulating film under the light absorption layer in this way, the second conductivity type impurity region can be protected. In addition, since the insulating film also functions as an antireflection film, it is possible to further reduce the possibility that the monitor light incident on the micropores of the light absorption layer is reflected.

  Moreover, it is preferable that each of the plurality of micropores has a predetermined area. When the area of the fine hole is defined, the area of the portion where the monitor light is incident on the light incident surface of the light detection element changes according to the number of the fine holes. When the area of the portion where the monitor light is incident changes, the light receiving sensitivity of the light detection element also changes, so that the light receiving sensitivity of the detection element can be adjusted.

Further, the area and the number of each of the plurality of micro holes are preferably set so that the photocurrent is not saturated when the amount of monitor light emitted from the light emitting element is 5 × 10 ⁻² W or less. By setting the area and number of each micropore in this way, the aperture ratio is set, and the value of the photocurrent output from the light detection element and the saturation characteristics are controlled in accordance with the change in the amount of light emitted from the monitor light. be able to.

  Moreover, it is preferable that the light emitting element test apparatus of this invention is further equipped with the thermostat which accommodates a light emitting element and a photon detection element. In this case, the characteristics of the light emitting element can be evaluated in a state where the light emitting element and the light detecting element are maintained at a desired temperature.

The light-detecting element for a light-emitting element test apparatus according to the present invention is housed in a thermostatic chamber together with the light-emitting element, and is disposed to face the light- emitting element. A light absorption layer having a hole; a first conductivity type substrate; a second conductivity type impurity region formed on a portion of the upper surface of the substrate; and an insulating film formed on the impurity region. The light absorption layer is formed by applying the material of the light absorption layer on the insulating film or by a sputtering method. As described above, the characteristic evaluation test of the light emitting element is performed. Can be performed with high accuracy. As described above, the material of the light absorption layer is preferably black resin or polysilicon with an antireflection film. Furthermore, it is preferable that the aperture ratio prescribed | regulated by the sum total of the area of several micropores is set to 1 to 30%. As will be described in detail later, when the aperture ratio is set to 30%, the saturation characteristic can be improved by about three times, and when the aperture ratio is set to 1%, the saturation characteristic is reduced to about 100%. It can improve 100 times. Note that the improvement of the saturation characteristic means that the light input at the time of saturation becomes larger.

  According to the present invention, a characteristic evaluation test can be performed with high accuracy and downsizing can be achieved.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is a diagram showing a configuration of a light-emitting element test apparatus according to this embodiment.

  The light-emitting element test apparatus 1 includes a thermostatic chamber 2 that can be controlled by the temperature controller 4.

  The temperature in the thermostat 2 can be set relatively high (50 to 100 ° C.) and can be used for a life measurement test or the like. A plurality of semiconductor laser substrates 14 are provided in the thermostatic chamber 2. A plurality of semiconductor laser diodes (light emitting elements) 6 can be mounted on each semiconductor laser substrate 14.

  The reason why the temperature in the thermostatic chamber 2 is relatively high is to accelerate the deterioration and shorten the test period. In any case of the ACC (Automatic Current Control) test and the APC (Automatic Power Control) test, a photodiode capable of monitoring the optical output of the semiconductor laser diode 6 and accurately monitoring the optical output change of 1% or less is required.

  In addition to the semiconductor laser substrate 14, a plurality of photodiode substrates 16 are provided in the thermostatic chamber 2. A plurality of photodiodes (photodetecting elements) 10 are mounted on the photodiode substrate 16. The photodiode 10 of this example is made of silicon and is disposed so as to face each semiconductor laser diode 6 mounted on the semiconductor laser substrate 14. As shown in FIG. 4, the light emitting end surface TS of the semiconductor laser diode 6 and the light incident surface IS of the photodiode 10 face each other. Further, the light emitting end face TS is perpendicular to the active layer AC of the semiconductor laser diode 6.

  More specifically, since the photodiode 10 monitors the optical output, in principle, all of the output light of the semiconductor laser diode 6 must be received. As shown in FIG. 4, the beam diameter of the monitor light L from the semiconductor laser diode 6 increases as the distance from the light exit surface end face TS increases. Since this divergence angle is relatively large, the beam diameter increases when the semiconductor laser diode 6 and the photodiode 10 are separated from each other. This beam diameter is equal to the product of the spread angle of the far-field image of the semiconductor laser diode 6 and the distance from the chip surface of the semiconductor laser diode. Therefore, in order to reduce the beam diameter of the light of the semiconductor laser, the photodiode 10 is disposed opposite to the semiconductor laser diode 6 so as to be close to each other.

  The semiconductor laser control unit 8 of the light emitting element test apparatus 1 can control the drive current supplied to each semiconductor laser diode 6 to be constant. Each semiconductor laser diode 6 mounted on the semiconductor laser substrate 14 emits monitor light when a drive current is supplied from the semiconductor laser control unit 8.

  The monitor lights emitted from the respective semiconductor laser diodes 6 are detected by the respective light detecting elements 10 arranged so as to face each other.

  The photodiode control unit 12 can measure a change in the photocurrent of each photodiode 10 when the driving current is constant (ACC test). The photodiode control unit 12 can measure a change in the drive current when the drive current is controlled so that the photocurrent output from the photodiode 10 is constant (APC test).

  For example, when an ACC test is performed under a certain condition, the time until the photocurrent decreases by A% is measured as the lifetime, and when the APC test is performed, the time until the drive current increases by B% is measured as the lifetime. .

  In order to accurately execute such a test, it is necessary that the amount of light incident on the photodiode 10 and the photocurrent (output current) have a linear relationship, and the photocurrent is increased with respect to the increase in the amount of incident light. When saturated, the photocurrent does not change even if the drive current is changed, and the drive current can take a plurality of values so that the photocurrent is constant, and an accurate test cannot be performed. .

  In this apparatus, the linearity of the output current with respect to the incident light amount can be maintained within a specific incident light amount range.

  FIG. 2 is a diagram for explaining the operation of the photodiode 10.

  When the photodiode 10 receives the monitor light L emitted from the semiconductor laser diode 6 facing it, the photodiode 10 outputs a photocurrent having a value corresponding to the amount of incident light to the photodiode controller 12. A bias voltage VR is connected in series to the cathode 10a side of the photodiode 10, and a load resistor RL is connected to the anode 10b side.

    As described above, the light emitting element testing apparatus 1 includes the photodiode 10 that receives the monitor light emitted from the semiconductor laser diode 6 and outputs a photocurrent, and the driving current to the semiconductor laser diode 6 or the photocurrent from the photodiode 10. Based on the above, the characteristic evaluation test of the semiconductor laser diode 6 is performed. The thermostatic chamber 2 houses the semiconductor laser diode 6 and the photodiode 10, and the characteristics of the semiconductor laser diode 6 can be evaluated in a state where the semiconductor laser diode 6 and the photodiode 10 are maintained at a desired temperature. That is, the above-described apparatus can be used when performing a characteristic (screening) test in a thermostatic chamber while controlling the light output to be constant during the characteristic test of the semiconductor laser diode.

  FIG. 3 is a plan view of the photodiode 10.

  A light absorption layer 10e is provided on the entire light incident surface of the photodiode 10 except for the electrode pads (cathode 10a, anode 10b). The light absorption layer 10e allows a part of the monitor light to be incident on the light incident surface. And have a plurality of fine holes (micro openings) 10c for receiving light. The anode 10b is provided so as to surround the periphery of the photodiode 10 chip.

  The monitor light emitted from the semiconductor laser diode 6 enters the light absorption layer 10e. The monitor light that has entered the portion of the light absorption layer 10e other than the fine hole 10c is absorbed by the light absorption layer 10e, and the monitor light that has entered the fine hole 10c reaches the light incident surface of the photodiode 10. Therefore, the light absorption layer 10e reduces the generation of reflected light.

  Even when the monitor light is reflected on the light incident surface, the inner wall surface of the minute hole 10c is the light absorbing layer 10e, so that the reflected light is absorbed by the inner wall surface of the minute hole 10c. . In the photodiode 10, the light absorption layer 10e suppresses the generation of reflected light and absorbs the reflected light even when the reflected light is generated. Therefore, since the possibility that the reflected light returns to the semiconductor laser diode 6 is reduced, the characteristic evaluation test of the semiconductor laser diode 6 can be accurately performed.

  Each of the plurality of micro holes 10c has a predetermined area (S). When the area S of the fine hole 10c is defined, the area of the portion where the monitor light is incident on the light incident surface of the photodiode 10 changes according to the number N (S × N) of the fine holes 10c.

When the shape of the fine hole 10c is a polygon, the diameter of the fine hole can be twice the average value of the distance from the center of gravity to the constituent points of each side, and the number of vertices of the polygon is infinite That is, when the shape of the fine hole 10c is a circle, the area S = πr ² (r = R / 2, R is the diameter of the fine hole).

  In this example, the area S of all the fine holes 10c is equal, and the number N is set in consideration of the amount of reflected light absorbed by the inner wall surface.

  As an example, the shape of the fine hole is circular, its diameter R is 20 μm, and the aperture ratio α in the light incident surface (= total area of fine holes (S × N) / light incident surface area T) is 10% and 20%. , 30%. In this case, the distance between the gravity center positions of the fine holes on the light incident surface is about 50 μm, about 40 μm, and about 30 μm, respectively.

  When the area (S × N) of the portion where the monitor light enters changes, the light receiving sensitivity of the photodiode 10 also changes, so that the light receiving sensitivity and saturation characteristics of the photodiode 10 can be adjusted.

That is, the area S and the number N of each of the plurality of fine holes 10c are set so that the photocurrent is not saturated with the amount of emitted monitor light from the semiconductor laser diode 6. As will be described in detail later, in the example shown in FIG. 10, when the resistance value of the load resistor RL is 100Ω and the bias voltage VR = 2V, a photodiode having an aperture ratio of 100% has an output light amount of 4 × 10 ^{− In} contrast to the saturation at ² W, the photodiode 10 with an aperture ratio of 10% did not saturate the amount of emitted monitor light up to 3 × 10 ⁻¹ W, and the saturation characteristics of the photodiode could be improved.

  Furthermore, it is preferable that the pitch of the fine holes (the distance between the positions of the center of gravity) be as small as possible. In this case, the sensitivity uniformity can be improved.

  By setting the area S and the number N of each microhole 10c in this way, the photocurrent output from the photodiode 10 and the saturation characteristics can be controlled in accordance with the change in the amount of emitted monitor light.

  Semiconductor laser diodes are rapidly increasing in output, and in the future, one with a single semiconductor laser output exceeding 1 W is expected to be commercialized. Normally, the output light from a semiconductor laser diode is detected by a photodiode, but the received light intensity is saturated for incident light intensity that exceeds the permissible received light intensity. By adjusting the aperture ratio using the layer 10e, such a problem can be solved.

  Further, in this apparatus, since the light absorption layer 10e having the fine hole 10c is provided on the light incident surface of the photodiode 10, it is not necessary to use an optical filter (ND filter) for dimming the monitor light.

  Here, the problem of the ND filter is added.

  That is, conventionally, an ND filter has been interposed in front of the photodiode. However, when the ND filter is disposed on a plane perpendicular to the optical axis of the semiconductor laser diode, the semiconductor laser diode light is reflected on the surface of the ND filter, The reflected light returns to the semiconductor laser diode and causes a malfunction.

  In such a case, the normal line to the surface of the ND filter may be inclined at a predetermined angle with respect to the optical axis of the laser beam emitted from the laser beam emitting end face of the semiconductor laser diode. With such a configuration, it is possible to prevent the monitoring laser light reflected on the surface of the ND filter from entering the laser light emitting end face as return light.

  In this case, a space for arranging the ND filter obliquely is required between the semiconductor laser diode and the photodiode, and the apparatus becomes large. Further, it is necessary to incline the ND filter, and the assembly becomes complicated because it is necessary to provide a fixing jig or the like.

  In addition, when the plurality of semiconductor laser diodes described above are arranged in parallel and tested simultaneously, the reflected light reflected from the filter surface returns to the adjacent semiconductor laser diode because the filter is inclined at a predetermined angle. May end up.

  In the above-described apparatus, the installation space for the ND filter is not required, and thus the size can be reduced. That is, the semiconductor laser diodes can be arranged with high density. That is, when the light incident surface of the photodiode 10 is an XZ plane, the pair of the semiconductor laser diode 6 and the photodiode 10 can be arranged in a direction (Y-axis direction) perpendicular to the XZ plane. When the number of photodiodes 10 (semiconductor laser diodes 6) in the X-axis direction is x, the number in the Y-axis direction is y, and the number in the Z-axis direction is z, the number of pairs of the semiconductor laser diode 6 and the photodiode 10 is xxy. Xz, enabling three-dimensional integration.

  In addition, since the ND filter adjusts the light attenuation rate by its thickness and requires strict manufacturing, the light absorption layer adjusts the light attenuation rate by the number and size of holes. Can do. Since the hole is processed by photolithography, it can be performed with high precision and no variation. Therefore, the photodiode can be easily manufactured.

Various materials can be considered for the light absorption layer 10e. In this example, (1) black resin and (2) polysilicon will be described.
(1) Black resin

  FIG. 5 is a cross-sectional view of the photodiode 10 when the light absorption layer 10e is a black resin (black photoresist).

  In this example, the material of the light absorption layer 10e contains black resin. When the black resin is a black photoresist, a commercially available photoresist in which a black dye or pigment is mixed into the photosensitive resin can be used. There are two types of photoresists: positive type and negative type. In the positive type, the exposed part of the resist is dissolved and removed by the developer, and the pattern remains on the photodiode wafer.

  When a black resin is used as the material of the light absorption layer 10e, it is possible to absorb the light components in the visible light region and the near infrared region among the components of the monitor light with the black resin layer. Therefore, generation | occurrence | production of reflected light can be suppressed more reliably. In addition, an appropriate material may be mixed as needed.

The photodiode 10 includes a semiconductor substrate 10f made of first conductivity type silicon, a high concentration second conductivity type impurity region 10g formed on a part of the upper surface of the substrate 10f, and an insulating film formed on the impurity region 10g. (SiO ₂ ) 10h, and the light absorption layer 10e is formed on the insulating film 10h. A high-concentration first conductivity type impurity region 10i is formed around the second conductivity type impurity region 10g, and an electrode pad 10b and an electrode pad 10a are provided respectively. A high-concentration first conductivity type impurity layer 10j is formed on the back surface of the substrate 10f.

  In this example, the first conductivity type is n-type and the second conductivity type is p-type, but the reverse is also possible. The interface between the substrate 10f and the impurity region 10g constitutes a PN junction, and the PN junction constitutes a light detection region, and a semiconductor surface located on this region is a light incident surface.

  By providing the insulating film 10h under the light absorption layer 10e, the second conductivity type impurity region 10g can be protected. In addition, since the insulating film 10h also functions as an antireflection film, the possibility that the monitor light L incident on the fine hole 10c of the light absorption layer 10e is reflected can be further reduced.

  The entire surface including the light incident surface of the photodiode 10 is covered with a black resin layer as a light absorption layer 10e that absorbs light in the near infrared region and visible region, but electrode pads (cathode 10a, anode 10b). Only exposed. In the black resin layer formed on the light incident surface of the photodiode 10, as an example, a plurality of micro holes 10c penetrating to the surface of the photodiode 10 are uniformly arranged so that the dot diameter is 20 μm and the aperture ratio is 10%. .

  Most of the monitor light L emitted from the semiconductor laser diode 6 is absorbed by the light absorption layer 10e made of a black resin layer, and only part of the monitor light L reaches the light incident surface through the fine hole 10c. Converted to photocurrent. Therefore, the received light output does not saturate with respect to the incident light intensity exceeding the allowable received light intensity, and the output of the semiconductor laser diode 6 can be accurately monitored. In addition, since the black resin layer as the light absorption layer 10e has a very low reflectance, the reflected light on the surface of the light absorption layer 10e is small, and the return light to the light emitting end face of the semiconductor laser diode 6 can be suppressed.

An antireflection film made of SiO ₂ (silicon oxide), Si ₃ N ₄ (silicon nitride), or the like is formed between the light incident surface and the black resin layer, so that the light of the semiconductor laser diode 6 can be further increased. Return light to the exit end face can be suppressed. That is, the above-described SiO ₂ layer and Si ₃ N ₄ layer also function as an antireflection film.
(2) Polysilicon

  FIG. 6 is a cross-sectional view of the photodiode 10 when the light absorption layer 10e is polysilicon.

An insulating film (SiO ₂ ) 10h is formed on the surface excluding the impurity region 10g of the substrate 10f, that is, on the peripheral region of the substrate, and the surfaces of the insulating film 10h and the impurity region 10g serve as a first antireflection film. The insulating film (Si ₃ N ₄ ) is covered with 10k. The light absorption layer 10e is formed on the insulating film 10k.

The light absorption layer 10e is made of polysilicon and covers the light incident surface of the photodiode 10 (only the electrode pads 10a and 10b are exposed). A second antireflection film 10m made of Si ₃ N ₄ is formed on the surface of the light absorption layer 10e. In this case, reflection of monitor light on the surface of the light absorption layer 10e can be prevented, and the semiconductor Return light to the light emitting end face of the laser diode 6 can be suppressed.

  The other configuration is the same as that of the black resin.

  When polysilicon is used as the material of the light absorption layer 10e, it is possible to absorb the ultraviolet light component among the components of the monitor light. Therefore, generation | occurrence | production of reflected light can be suppressed more reliably.

  Next, a method for manufacturing the photodiode 10 will be described.

  FIG. 7 is a diagram for explaining a method of manufacturing the photodiode 10 when a black resin is used as the light absorption layer 10e.

  First, as shown in FIG. 7A, a 5 mm × 5 mm rectangular semiconductor substrate 10f made of silicon of the first conductivity type is prepared. Here, the first conductivity type is n-type, and the thickness of the substrate 10f is 0.3 mm. Actually, the semiconductor substrate 10f is a semiconductor wafer, and a rectangular formation region of 5 mm × 5 mm is set on the surface of the semiconductor wafer.

  Next, as shown in FIG. 7B, a mask is formed on the central region so that a peripheral region (planar rectangular ring) on the surface of the semiconductor substrate 10f is opened, and an n-type impurity (this example) In this case, phosphorus is added into the peripheral region (planar rectangular ring) of the semiconductor substrate 10f to form the impurity region 10i in the peripheral region on the surface side of the substrate 10f. Further, an n-type impurity (phosphorus in this example) is also added to the entire back surface of the semiconductor substrate 10f in the semiconductor substrate 10f, thereby forming an impurity layer 10j on the back surface side. Insulating films 10h and 10x are formed on the front and back surfaces of the substrate 10f, respectively. In this example, the insulating films 10h and 10x are formed by thermally oxidizing silicon.

  The impurity region 10i and the impurity layer 10j were set to have a surface resistivity ρ = 12Ω / sq and a depth xj = 1.5 μm, respectively.

  Thereafter, as shown in FIG. 7C, the second conductivity type impurity is added into the central region of the surface of the semiconductor substrate 10f to form an impurity flow region 10g in a planar rectangular shape. Here, the second conductivity type is p-type. The additive in this example is boron, and the surface resistivity ρ = 44Ω / sq and the junction depth xj = 0.55 μm were set. The p-type impurity can be added by an ion implantation method through the insulating film 10h. In addition, thermal oxidation is performed after addition.

  Next, as shown in FIG. 7D, a plurality of contact holes are formed in the insulating film 10h on the surface side, and electrode pads 10a and 10b that are in contact with the impurity regions 10i and 10g, respectively, are formed in these contact holes. It is formed with a thickness of 1 μm. These contact holes are formed by covering a region other than the contact hole formation position with a mask such as a photoresist and etching the insulating film 10h in the opening of the mask with a hydrofluoric acid aqueous solution or the like. The electrode pads 10a and 10b can be formed by vapor deposition of aluminum. The insulating film 10x on the back side is removed.

  Finally, as shown in FIG. 7 (e), a black photoresist is applied on the insulating film 10h on the substrate surface, and this is exposed and developed to have a plurality of fine holes on the impurity region 10g, and A light absorption layer 10e having a thickness of 1.2 μm is formed with the electrode pads 10a and 10b exposed.

  FIG. 8 is a diagram for explaining a method of manufacturing the photodiode 10 when polysilicon is used as the light absorption layer 10e.

  First, as shown in FIG. 8A, a 5 mm × 5 mm rectangular semiconductor substrate 10f made of silicon of the first conductivity type is prepared. Here, the first conductivity type is n-type, and the thickness of the substrate 10f is 0.3 mm. Actually, the semiconductor substrate 10f is a semiconductor wafer, and a rectangular formation region of 5 mm × 5 mm is set on the surface of the semiconductor wafer.

  Next, as shown in FIG. 8B, a mask is formed on the central region so that a peripheral region (planar rectangular ring) on the surface of the semiconductor substrate 10f is opened, and an n-type impurity (this example) is formed on the mask. In this case, phosphorus is added into the peripheral region (planar rectangular ring) of the semiconductor substrate 10f, and the impurity region 10i is formed in the peripheral region on the surface side of the substrate 10f. Further, an n-type impurity (phosphorus in this example) is also added to the entire back surface of the semiconductor substrate 10f in the semiconductor substrate 10f, thereby forming an impurity layer 10j on the back surface side of the substrate. Insulating films 10h 'and 10x are formed on the front and back surfaces of the substrate 10f, respectively. In this example, the insulating films 10h 'and 10x are formed by thermally oxidizing silicon.

  The impurity region 10i and the impurity layer 10j were set to have a surface resistivity ρ = 12Ω / sq and a depth xj = 1.5 μm, respectively.

  After that, as shown in FIG. 8C, a mask is formed so that the central region of the surface of the semiconductor substrate 10f is opened, and a second conductivity type impurity is added into the central region to form a planar rectangular shape. Impurity region 10g is formed. Here, the second conductivity type is p-type. The additive in this example is boron, and the surface resistivity ρ = 44Ω / sq and the junction depth xj = 0.55 μm were set. The p-type impurity can be added by an ion implantation method through the insulating film 10h.

After the addition of the p-type impurity, the insulating film 10h ′ on the impurity region 10g is etched through a mask (using an etchant such as an aqueous hydrofluoric acid solution), and then, on the entire surface of the substrate, The first antireflection film 10k, the light absorption layer 10e ′, and the second antireflection film 10m ′ are sequentially formed. The first antireflection film 10k is Si ₃ N ₄ having a thickness of 47 nm formed by sputtering, the light absorption layer 10e ′ is polysilicon having a thickness of 400 nm formed by sputtering, and the antireflection film 10m ′. Is 47 nm thick Si ₃ N ₄ formed by sputtering.

  Next, as shown in FIG. 8D, a mask is formed on the substrate so that the light absorption layer 10e having the plurality of fine holes 10c and the second antireflection film 10m remain only on the central region of the substrate surface. Then, the substrate is dry-etched through this mask. That is, a photoresist is applied on the second antireflection film 10m ′ on the substrate surface, and this is exposed and developed to have a plurality of fine holes on the impurity region 10g, and a peripheral region on the substrate surface is opened. After the pattern mask is formed, etching is performed.

_Si 3 _{N 4} which constitutes the second anti-reflection film 10m, for example, can be etched using a plasma etch using CF ₄ and oxygen, the polysilicon constituting the light-absorbing layer 10e also CF ₄ and oxygen Etching can be performed using the plasma etch used.

  If the upper second antireflection film 10m is completely removed, the polysilicon constituting the light absorption layer 10e can be etched by wet etching with a hydrofluoric acid aqueous solution or the like.

  Finally, as shown in FIG. 8E, a plurality of contact holes are formed in the insulating film 10k on the surface side, and electrode pads 10a and 10b that are in contact with the impurity regions 10i and 10g, respectively, are formed in these contact holes. It is formed with a thickness of 1 μm. These contact holes are formed by covering a region other than the contact hole formation position with a mask such as a photoresist, and dry etching the insulating film 10h and the first antireflection film 10k in the opening of the mask. The electrode pads 10a and 10b can be formed by vapor deposition of aluminum.

  A light-emitting device test apparatus employing the photodiode 10 using the above-described black resin was manufactured, and the relationship between the amount of light incident on the photodiode 10 (W) and the output current (A) from the photodiode 10 was measured.

  The temperature of the thermostat 2 was set to 85 ° C. This is the standard temperature for the semiconductor laser diode 6 reliability test.

  FIG. 9 is a graph showing the relationship between the amount of light incident on the photodiode 10 (W) and the output current (A) from the photodiode 10.

  The wavelength of incident light was λ = 808 nm, the irradiation size was 3.7 mm × 3.7 mm, the resistance value of the load resistance RL was 100Ω, and the bias voltage VR = 0V. As the photodiode 10, one having an aperture ratio α of the light absorption layer 10 e of 100% (no light absorption layer), 30%, 20%, 10% was manufactured.

When the aperture ratio α is 10%, the photocurrent (output current) does not saturate and the linearity is maintained in the range where the emitted light amount of the monitor light (the incident light amount to the photodiode) is 8 × 10 ⁻² W or less. I understand that. Even when the aperture ratio is 20%, the linearity is substantially maintained and does not saturate in the range where the incident light quantity is 4 × 10 ⁻² W or less, and the incident light quantity is 2 × 10 ⁻² even when the aperture ratio is 30%. It can be seen that the linearity is maintained in the range of W or less and does not saturate up to 4 × 10 ⁻² W.

On the other hand, when the aperture ratio α is 100%, the photocurrent is saturated when the amount of incident light is 8 × 10 ⁻³ W or more. When the aperture ratio α is 10%, the photocurrent does not saturate until the incident light quantity becomes 8 × 10 ⁻² W or more. Therefore, by setting the aperture ratio α to 10%, saturation characteristics (photodiodes exhibiting saturation) The amount of incident light) increases about 10 times. Further, when the aperture ratio α is 30%, the saturation characteristic is increased three times or more because the photocurrent does not saturate until the incident light quantity becomes 2 × 10 ⁻² W or more. From these facts, it is considered that the saturation characteristic increases about 100 times when the aperture ratio α is 1%.

  FIG. 10 is a graph showing the relationship between the amount of light incident on the photodiode 10 (W) and the output current (A) from the photodiode 10 when a bias voltage is applied.

  That is, the wavelength λ of incident light was 808 nm, the irradiation size was 3.7 mm × 3.7 mm, the resistance value of the load resistance RL was 100Ω, and the bias voltage VR = 2V.

When the aperture ratio α is 10%, the photocurrent (output current) does not saturate and the linearity is maintained in the range where the emitted light amount of the monitor light (the incident light amount to the photodiode) is 3 × 10 ⁻¹ W or less. I understand that. Even when the aperture ratio is 20%, the linearity is maintained and does not saturate in the range where the incident light quantity is 2 × 10 ⁻¹ W or less, and the incident light quantity is 7 × 10 ⁻² W even when the aperture ratio is 30%. It can be seen that linearity is maintained in the following range and does not saturate up to 1.5 × 10 ⁻¹ W. Thus, when the amount of incident light is 5 × 10 ⁻² W or less, the photocurrent is not saturated.

On the other hand, when the aperture ratio α is 100%, the photocurrent is saturated when the incident light quantity is 4 × 10 ⁻² W or more.

  In the case of an APC test using the above-described apparatus, the output current (photocurrent) of the photodiode 10 is detected, and the drive current of the semiconductor laser diode 6 is set so that the optical output of the semiconductor laser diode 6 becomes a constant output, for example, 1 W. The driving current of the semiconductor laser diode 6 is measured every certain time. Thereby, the presence or absence of a change in the output characteristics of the semiconductor laser diode 6 can be measured. As is clear from FIGS. 9 and 10, it is possible to prevent the incident light quantity from being saturated in a wide range up to about 1 W by setting the aperture ratio of the photodiode 10 low.

  As described above, in the above-described light emitting element test apparatus, the light receiving output of the photodiode 10 is not saturated, and the problem of return light to the semiconductor laser diode 6 does not occur, and the semiconductor laser diode 6 and the photodiode 10 are not affected. Can be arranged close to each other, and downsizing and high density of the semiconductor laser diode 6 can be realized.

  FIG. 11 is a cross-sectional view of a light detection element in which the photodiode 10 described above is molded. In this case, the light source is limited to visible or near infrared light.

  A photodiode 10 is disposed in the mount package 31, and the photodiode 10 is covered with a translucent resin 30 in which a scattering material 32 is dispersed.

  Since the scattering material 32 scatters light incident on the photodiode 10, sensitivity uniformity can be improved. The translucent resin 30 is made of a material that is transparent to incident light. The scattering material 32 is used by being dispersed in a resin.

  When the incident light is infrared, (A) the scattering material 32 is, for example, transparent silica having a size of several μm, and (B) the mold resin 30 is, for example, a transparent silicone resin or an epoxy resin.

  As the photodiode package, a photodiode packaged with a resin, a photodiode packaged with a photodiode in a ceramic package, or a resin package molded with a photodiode in a metal package can be considered. Further, the reflectance can be further reduced by plasma processing the surface of the light absorption layer 10e.

  In addition, the photodiode (light detecting element for light emitting element test apparatus) 10 according to the above-described embodiment includes a light absorption layer 10e having a plurality of fine holes on the light incident surface, and a characteristic evaluation test of the semiconductor laser diode 6 Can be performed with high accuracy. The aperture ratio α of the light absorption layer 10e defined by the total area of the plurality of micropores is preferably set to 1 to 30%. In this case, the saturation of the photocurrent with respect to the amount of incident light is suppressed. Can do. The reason why the preferable aperture ratio α is set to 1% or more is that the openings such as contact holes are structurally excluded.

It is a figure which shows the structure of the light emitting element test apparatus which concerns on this embodiment. FIG. 3 is a diagram for explaining the operation of the photodiode 10. 1 is a plan view of a photodiode 10. FIG. It is a figure which shows the positional relationship of a semiconductor laser diode and a photodiode. It is sectional drawing of the photodiode 10 in case the light absorption layer 10e is black resin (black photoresist). It is sectional drawing of the photodiode 10 in case the light absorption layer 10e is a polysilicon. It is a figure for demonstrating the manufacturing method of the photodiode 10 at the time of using black resin as the light absorption layer 10e. It is a figure for demonstrating the manufacturing method of the photodiode 10 at the time of using a polysilicon as the light absorption layer 10e. 2 is a graph showing the relationship between the amount of light incident on a photodiode (W) and the output current (A) from the photodiode. 3 is a graph showing the relationship between the amount of light incident on a photodiode (W) and the output current (A) from the photodiode 10 when a bias voltage is applied. 1 is a cross-sectional view of a light detection element in which a photodiode 10 is molded.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light emitting element test apparatus, 2 ... Constant temperature bath, 6 ... Semiconductor laser diode, 8 ... Semiconductor laser control part, 10 ... Photodiode, 10c ... Fine hole, 10f ... Semiconductor substrate, 10e ... Light absorption layer, 10g ... Impurity region, 10h: insulating film, 12: photodiode control unit, 14: semiconductor laser substrate, 16: photodiode substrate, IS: light incident surface, L: monitor light.

Claims (9)

A light-emitting element testing apparatus that includes a light-detecting element that receives monitor light emitted from a light-emitting element and outputs a photocurrent, and performs a characteristic evaluation test of the light-emitting element based on a drive current to the light-emitting element or the photocurrent Because
A thermostat housing the light- emitting element and the light-detecting element disposed opposite to the light-emitting element;
A light absorption layer is provided on the light incident surface of the light detection element,
The light absorption layer has a plurality of micro holes for receiving a part of the monitor light at the light incident surface, and the area and the number of each of the micro holes are the monitor light by the light emitting element. Is set so that the photocurrent does not saturate when the amount of emitted light is 5 × 10 ⁻² W or less, and the aperture ratio defined by the total area of the plurality of micropores is set to 1 to 30% And
The photodetecting element is
A first conductivity type substrate;
A second conductivity type impurity region formed in a portion of the upper surface of the substrate;
An insulating film formed on the impurity region;
Have
The light-absorbing layer is formed by applying a material of the light-absorbing layer on the insulating film or by a sputtering method.   The light emitting element testing apparatus according to claim 1, wherein the material of the light absorption layer includes a black resin.   The light emitting device testing apparatus according to claim 1, wherein a material of the light absorption layer is polysilicon.   4. The light emitting device testing apparatus according to claim 3, wherein the polysilicon of the light absorbing layer is provided with an antireflection film.   The light-emitting element test apparatus according to claim 4, wherein the antireflection film includes first and second antireflection films respectively provided on the upper and lower surfaces of the light absorption layer. A light-detecting element for a light-emitting element test apparatus that is housed in a thermostatic chamber together with a light-emitting element, is disposed opposite to the light-emitting element, and performs a characteristic evaluation test of the light-emitting element,
A light absorption layer having a plurality of micropores on the light incident surface, the aperture ratio defined by the total area of the plurality of micropores is set to 1 to 30%,
A first conductivity type substrate;
A second conductivity type impurity region formed in a portion of the upper surface of the substrate;
An insulating film formed on the impurity region;
Have
The light-absorbing layer is a light-detecting element for a light-emitting element test apparatus, which is formed by applying a material of the light-absorbing layer on the insulating film or by a sputtering method.   The light detection element for a light-emitting element test apparatus according to claim 6, wherein a material of the light absorption layer is a black resin.   The light detection element for a light emitting element test apparatus according to claim 6, wherein a material of the light absorption layer is polysilicon. 9. The light detection element for a light emitting element test apparatus according to claim 8, wherein the polysilicon of the light absorption layer is provided with an antireflection film.

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