JP2769744B2 - Image chip and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image chip having a large number of light receiving / emitting surfaces on one semiconductor substrate and a method for manufacturing the same. The present invention particularly relates to prevention of lateral displacement of an electrode with respect to a light receiving / emitting surface and detection thereof.

2. Description of the Related Art Image chips in which a large number of light receiving and emitting surfaces are provided and electrodes are stacked on each light receiving and emitting surface are well known. Such an image chip is obtained by integrating a large number of light emitting diodes and photodiodes, and is used for a head of an optical printer, a head of an image sensor, and the like.

The problem here is that if the alignment between the electrode and the light receiving / emitting surface is incorrect, the luminous efficiency and the light receiving efficiency are reduced. FIG. 9 shows a problem using a light emitting diode as an example. The light emitting diode 2 is under development by the inventor. In the figure, reference numeral 4 denotes a light emitting surface, and 6 denotes a diffusion preventing layer, which is used to prevent impurities from diffusing to the surroundings when the light emitting surface 4 is formed by impurity diffusion or the like. Things. Reference numeral 8 denotes an electrode, which crosses the center of the light emitting surface 4.

In the light emitting diode 2, even if the electrodes are shifted in the vertical direction in the figure, the positional relationship of the electrode 8 with respect to the light emitting surface 4 is constant.
It does not affect the luminous efficiency. If the displacement of the electrode 8 is significant, the luminous efficiency is reduced, but if the displacement is within the range of the play portion of the electrode 8 outside the light emitting surface 4, the luminous efficiency is not related.
However, in the light emitting diode 2 shown in FIG. 9, when the electrode 8 is shifted from the light emitting surface 4 in the horizontal direction in the figure, the luminous efficiency is reduced.

The reason why the light emitting surface 4 and the electrode 8 are shifted is that it is difficult to accurately align the semiconductor wafer and the electrode mask with each other. For example, in the conventional method, alignment is performed between the edge of the wafer and the edge of the electrode mask.

The inventor examined the light emitting diode 12 in FIG. 10 to prevent the influence of the lateral displacement. In the light emitting diode 12, the electrodes 18 are provided in a cross shape, and the luminous efficiency does not decrease even if the electrodes 18 are shifted in the vertical direction or the horizontal direction.

However, the portion covered with the electrode does not contribute to light emission. As shown in FIG. 10, when the electrode area is increased, the output of the light emitting diode is reduced. For this reason, there is a limit to the solution in the direction of complicating the electrode pattern.

FIG. 11 shows the characteristics of the light emitting diode 2 shown in FIG.
When the electrode 8 is located at the center of the light emitting surface 4, the light emission intensity distribution indicated by the solid line in the figure is obtained. When the electrode 8 is displaced in the horizontal direction, the characteristic becomes a dashed line, and the overall output of the light emitting diode 2 and the emission intensity distribution change.

When the output or the intensity distribution of the light emitting diode 2 fluctuates, in the case of an optical printer head, the center position of the dot shifts, and unevenness of density occurs for each dot.

[Problems of the Invention] An object of the present invention is to (1) improve the shape of an electrode to prevent the influence of vertical displacement of an electrode with respect to a light receiving / emitting surface, and (2) easily detect lateral displacement of an electrode with respect to a light receiving / emitting surface. (Claim 1).

Another object of the present invention is to provide a method of manufacturing an image chip in accordance with the above, and at the time of forming an electrode on a semiconductor wafer, to facilitate alignment between an electrode mask and a light emitting / receiving surface, to prevent lateral displacement of the electrode, It is to improve the yield of image chips.

[Constitution of the Invention] An image chip according to the present invention is an image chip in which a large number of light receiving and emitting surfaces are formed on a semiconductor substrate, and at least one electrode is laminated on each light receiving and emitting surface. And at least one lateral displacement detection surface, which has a specific positional relationship with the light receiving and emitting surface, is provided on the semiconductor substrate, and has a specific positional relationship with the electrode, and the electrode on the light receiving and emitting surface has The lateral displacement detection mark provided in the direction perpendicular to the direction is arranged near the lateral displacement detection surface.

In this specification, the light receiving / emitting surface means a place on an image chip where light is received / emitted, and is used in a different sense from a completed light emitting / receiving element.

Here, in order to realize a specific positional relationship between the light receiving / emitting surface and the lateral displacement detection surface, these may be simultaneously manufactured using the same mask. The positional relationship between the electrode and the lateral displacement detection mark can be realized by simultaneously manufacturing the electrode and the lateral displacement detection mark using the same mask.

The lateral displacement detecting surface may be provided separately from the light receiving / emitting surface. However, it is better to use the light receiving / emitting surface as the lateral displacement detection surface as it is,
Since the deviation between the actual electrode and the actual light receiving / emitting surface can be detected, more direct detection can be performed. When the lateral displacement detection surface is provided separately from the light receiving / emitting surface, for example, when mounting the image chip on the substrate, a marker for detecting the position of the light receiving / emitting surface is provided at the same time as the light receiving / emitting surface, and this is also used as the lateral displacement detection surface. Just do it.

When the light receiving / emitting surface is also used as the lateral displacement detection surface, it is preferable to provide the lateral displacement detection mark at a predetermined distance from the light receiving / emitting surface so that the lateral displacement detection mark does not enter the inside of the light receiving / emitting surface. A cause of the lateral displacement detection mark entering the light receiving / emitting surface is a vertical displacement of the detection mark. The distance between the detection mark and the light emitting / receiving surface may be, for example, about twice as long as the positioning accuracy in the vertical direction as a reference and the positioning error.

For example, a scale in a direction parallel to the electrodes is engraved on both ends of the lateral displacement detection mark. Both ends are emphasized by the scale, so that the end of the detection mark can be easily checked and the degree of the lateral shift can be read from the scale. Alternatively, both ends of the lateral displacement detection mark may be shortened by a predetermined distance from both ends of the light receiving and emitting surface to detect whether the detection mark protrudes from the end of the light receiving and emitting surface. In this case, the detection mark is from the light receiving / emitting surface,
For example, the positioning error is shortened by the allowable error, and it is detected whether or not there is a deviation exceeding the allowable error.

The method for manufacturing an image chip according to the present invention is as follows.

(1) A large number of light receiving / emitting surfaces are formed on a semiconductor wafer; (2) an electrode material layer and a photoresist layer are sequentially provided on substantially the entire surface of the wafer; And forming a lateral displacement detection mark in a direction perpendicular to the electrode direction on the light receiving / emitting surface on the electrode mask near the lateral displacement detection surface, and (4) aligning the lateral displacement detection mark with the lateral displacement detection surface to form an electrode mask. (5) Next, the photoresist layer is exposed to light using an electrode mask to form an electrode crossing the center of the light emitting / receiving surface.

Hereinafter, an embodiment will be described using an image chip in which light emitting diodes are integrated as an example.

[Embodiment] In FIG. 1, reference numeral 2 denotes a light emitting diode, for example, which is arranged on a single image chip in approximately 64 lines.
Reference numeral 4 denotes a light emitting surface, 6 denotes a peripheral diffusion preventing layer, and 8 denotes an electrode crossing the center of the light emitting surface 4. The light emitting surface 4 is 50 μm (electrode 8
) × 60 μm (direction parallel to the electrode 8). The light emitting surfaces 4 were arranged at a density of 300 per inch. The electrode 8 does not have to penetrate the light emitting surface 4 and may be stopped just before the end face on the opposite side of the light emitting surface 4 when viewed from the base side of the electrode 8. However, in this case, the allowable width of the electrode 8 to vertical displacement is reduced.

Reference numeral 20 denotes a lateral displacement detection mark which is provided perpendicular to the electrode 8 and is arranged at a position 10 μm away from the end of the light emitting surface 4 and in parallel with the end of the light emitting surface 4. The vertical accuracy of the electrode 8 in the embodiment is 10μ.
m, and the mark 20 was separated by an interval corresponding to this, so that the mark 20 did not enter the light emitting surface 4. A plurality of graduations 22 were cut at both ends of the mark 20 at intervals of about 5 μm, and both ends were aligned with the end of the light emitting surface 4. When the alignment between the electrode 8 and the light emitting surface 4 is perfect, the end of the mark 22 is aligned with the end of the light emitting surface 4, and when the alignment is inaccurate, the degree of the lateral displacement is read by the scale 22. 5 μm is an allowable error for the lateral displacement.

The detection mark 22 is located on the base side of the electrode 8 (the lower side in the figure).
And may be cut off from the electrode 8.
Further, the electrode may have a projection at the center as shown in FIG. In FIG. 2, 32 is a light emitting diode, and 38 is an electrode.

The vertical and horizontal directions in this specification are the vertical direction on the light emitting surface 4 of the electrode 8 in FIG. 1 and the horizontal direction in FIG.

FIG. 3 shows an example in which both ends of the detection mark 40 are shorter than the light-emitting surface 4 by an interval A. Here, the interval A is an allowable error of 5
μm, if a lateral displacement exceeding 5 μm occurs, the mark 40
Is overlapped with the end of the light emitting surface 4. The mark 40 indicates that the light emitting surface 4 has a lateral displacement exceeding the allowable error of 5 μm.
Is detected from exceeding the end of. Although it is more difficult to recognize the position, the end of the mark 40 is
It is also possible to detect a lateral displacement by extending the mark 40 by μm and entering the end of the mark 40 inside the light emitting surface 4.

In any of the embodiments, the lateral displacement detection marks are provided on all the light emitting surfaces 4, but may be provided on at least one light emitting surface. Confirmation of electrode position among 64 light emitting surfaces 4
This is because it is only necessary to confirm three or four light emitting surfaces 4.

4 to 8 show the manufacturing process of the embodiment of FIG. An n-type Ga-As-P layer 42 is epitaxially grown on an n-type Ga-As substrate 40. Next, a diffusion preventing layer 6 such as SiO ₂ or Si ₃ N ₄ is laminated (FIG. 4). The diffusion preventing layer 6 is etched through a photoresist to provide an impurity diffusion window, and a p-type impurity such as Zn is diffused to form the light emitting surface 4. p
The junction between the light emitting surface 4 of the mold diffusion layer and the Ga-As-P n-type layer 42 is a light emitting portion, and emits light by a current flowing therein.

Al electrode material layer 44 is deposited on almost the entire surface of the wafer of Ga-As substrate 400, and a photoresist layer 46 is applied (FIG. 5). The electrode material layer 44 has an edge E around the light emitting surface 4 due to a step between the light emitting surface 4 and the diffusion preventing layer 6. Since the photoresist layer 46 is transparent, the step E can be seen with a microscope, and the step E is used for alignment. next,
The electrode 8 and the lateral displacement detection mark 20 are formed using an electrode mask. This process is shown in FIG.

In FIG. 6, reference numeral 50 denotes a wafer, and cells are image chips.
Corresponds to 52. Reference numeral 54 denotes a mark for roughly aligning the wafer 50 with the electrode mask. The electrode mask and the wafer 50 are roughly aligned using the alignment mark 54. Next, a step E around the light receiving / emitting surface 4
Then, the position of the light receiving / emitting surface 4 is detected, and the position of the wafer 50 is finely adjusted. That is, in several places on the wafer 50, alignment is performed using the lateral displacement detection mark 21 and the step E above the light receiving / emitting surface 4, and if there is an error, the value is read from the scale 22, and the alignment is performed. 7).

After the alignment, the photoresist layer 46 is exposed and the electrodes 8 are formed by etching (FIG. 8). Further, a common electrode is formed on the back surface of the wafer.

Thereafter, the wafer 50 is cut, and the image chips 52 are cut out. With respect to the cut out image chip 52, the lateral displacement of the electrode is detected for each image chip again using the lateral displacement detection mark 20, and defective products are excluded.

[Effects of the Invention] According to the invention of claim 1, (1) by improving the electrode shape, the effect of vertical displacement of the electrode with respect to the light receiving and emitting surface is prevented, and (2) detection of lateral displacement of the electrode with respect to the light receiving and emitting surface. make it easier.

According to the second aspect of the present invention, at the time of forming an electrode on a semiconductor wafer, alignment between an electrode mask and a light receiving / emitting surface is facilitated,
It prevents lateral displacement of the electrodes and improves the yield of image chips.

[Brief description of the drawings]

 1 to 3 are plan views of a main part of the embodiment, respectively, FIGS. 4 and 5 are cross-sectional views showing manufacturing steps of the embodiment, FIG. 6 is a plan view showing manufacturing steps of the embodiment, FIG. 7 is a plan view of a main part showing a manufacturing process of the embodiment, FIG. 8 is a cross-sectional view showing a manufacturing process of the embodiment, FIGS. 9 and 10 are cross-sectional views of a conventional example, and FIG. FIG. In the figure, 4 ... light emitting surface, 6 diffusion prevention layer, 8,18,34 ... electrode, 20,40 ... lateral displacement detection mark, 22 ... scale.

Claims (2)

(57) [Claims] 1. An image chip having a plurality of light receiving / emitting surfaces formed on a semiconductor substrate and at least one electrode laminated on each light receiving / emitting surface, wherein the electrodes have a shape crossing a central portion of the light receiving / emitting surface. At least one lateral displacement detection surface having a specific positional relationship with the light receiving and emitting surface is provided on the semiconductor substrate, and has a specific positional relationship with the electrode and in a direction perpendicular to the direction of the electrode on the light receiving and emitting surface. An image chip, wherein the provided lateral displacement detection mark is arranged near a lateral displacement detection surface. 2. A method of manufacturing an image chip, comprising: providing a large number of light receiving / emitting surfaces and cutting out a large number of image chips from one semiconductor wafer having at least one electrode laminated on each light receiving / emitting surface; After forming a large number of light receiving and emitting surfaces on the wafer, an electrode material layer and a photoresist layer are sequentially provided on almost the entire surface of the semiconductor wafer, and then the photoresist is formed using an electrode mask having an electrode pattern crossing the center of the light receiving and emitting surface. When exposing the layer to form an electrode that crosses the center of the light receiving and emitting surface, a semiconductor wafer is provided with a lateral displacement detection surface at the same time as the light receiving and emitting surface, and an electrode mask near the lateral displacement detecting surface is provided with a light receiving and emitting surface. A lateral displacement detection mark in the direction perpendicular to the electrode direction is provided, and the lateral displacement detection mark is aligned with the lateral displacement detection surface to prevent lateral displacement of the electrode with respect to the light receiving / emitting surface. Also, a method for manufacturing an image chip.