JPH0624040A - Recognition of led array reference pattern and detection of position of led array using the recognition - Google Patents

Abstract

PURPOSE:To provide an LED print head wherein shift of pitch and step difference at light emitting part among LED arrays are only a little, relating to LED arrays to be used as an optical writing exposure light source of an electrophotographic printer. CONSTITUTION:By utilizing a characteristic that reflection factor in an area of a select diffusion mask 203 formed on the surface of an LED array 201 largely varies dependent on wave length, reflection factor intensity distributions a1, and b1 on the surface of the LED array are measured by two different waves. A difference between the surface patterns a1 and b1 is obtained and binarized, so that a pattern of a position detecting window 207 formed on the surface of the LED array 201 or a light emitting section 204 is recognized as a reference pattern and a position at die bonding is corrected by the position information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recognizing a reference pattern used for positioning an LED array used as an optical writing exposure light source of an electrophotographic printer and a method of detecting the position of the LED array using the reference pattern recognition method. It is about.

[0002]

2. Description of the Related Art An LED printhead is composed of a plurality of LEDs.
Arrays are arranged in a regular array. The process of arranging the LED arrays is called dice bonding, and the positional relationship of the LED arrays after the dice bonding process is shown in FIG.

As shown in FIG. 2, a normal LED array 101 is provided.
Alternatively, the pitch P of the light emitting portions 104 within the 102 is determined by the photolithography precision when forming the light emitting portions 104, and therefore is kept highly accurately constant.

However, the pitch P'of the light emitting portion 104 between the LED arrays 101 and 102 is greatly affected by the mechanical accuracy of arranging the LED arrays at the time of die bonding, so P '= P
However, there is a possibility that it will shift significantly. Further, as shown in FIG. 2, the light emitting unit 104 may be displaced by t ′.

These deviations cause deterioration in print quality when mounted on a printer and printed. If the pitch P'expands, it becomes a vertical white streak, and if it becomes narrow, it becomes a vertical black streak. Then, when t ′ becomes large, a step is generated on the horizontal line.

Therefore, conventionally, as shown in FIG.
Taking advantage of the difference in the total reflectance of the pattern on the array surface,
The position of the LED array was detected. FIG. 4 is A- of FIG.
It is a total reflectance distribution in the A section. Then, the portion of the reflectance indicated by the dotted line that is equal to or higher than a certain constant binarization threshold value is extracted, and the position of the LED array is detected by image recognition,
After obtaining the shift amount, the die bonding was performed while performing the correction to prevent the pitch P ′ between the LED arrays and the step t ′ from shifting as much as possible.

The image recognition process will be described below. FIG. 3 is a sectional view showing an AA section of the LED array 101. In FIG. 3, a selective diffusion mask 105 is provided on the N-type semiconductor substrate 106, a window serving as the light emitting portion 104 is opened therein, and P-type impurities are diffused to form a P-type diffusion layer 105. And
An Al wiring pattern 103 is formed on the selective diffusion mask 105 and is connected to the P type diffusion layer 105 as shown in the region B. In the conventional image recognition, the Al wiring pattern 103 has the highest reflectance among these patterns, and therefore the image after binarization has only the Al wiring pattern 103 as the reference pattern 108 as shown in FIG. Was recognized.
Then, the position of the light emitting portion 104 is detected based on the predetermined relative positional relationship between the Al wiring pattern 103 and the light emitting portion 104.

[0008]

Therefore, according to the conventional position detecting method, when the Al wiring pattern 103 is formed deviated from the light emitting portion 104, the deviated Al wiring pattern 103 is recognized as the reference pattern 108, From this position, the light emitting unit 104
Since the position of the light emitting unit 104 is estimated and corrected,
P'is not P '= P, and the step t'may be large. Moreover, since the formation of the Al wiring pattern 103 and the pattern formation of the light emitting portion 104 are performed in different photolithography steps, there is a high possibility that the two will be misaligned due to misalignment of the mask.

Although the case where Al (aluminum) is used as the wiring pattern has been described here, other metals,
For example, the same problem occurs when the wiring pattern is formed of Au (gold) or the like.

The present invention eliminates the above-mentioned problem that the position of the light emitting portion is not always accurately positioned because the position correction during die bonding is performed by recognizing the wiring pattern as the reference pattern. It is an object of the present invention to provide an LED print head in which the pitch of the light emitting portion between LED arrays and the level difference are extremely small.

[0011]

The present invention utilizes the property that the reflectance of the selective diffusion mask region formed on the LED array surface greatly differs depending on the wavelength, and the reflectance of the LED array surface depends on two different wavelengths. Is measured and the position of the light emitting portion formed on the LED array surface is detected by the step of detecting the surface pattern according to each wavelength and the step of obtaining the difference between the two surface patterns detected by the step. The light emitting unit itself is recognized as a reference pattern, and the position correction at the time of die bonding is performed based on this position information.

Specifically, a semiconductor substrate and a selective diffusion mask made of a dielectric thin film formed on the semiconductor substrate,
In an LED array having a light emitting portion formed on the semiconductor substrate exposed in an opening formed in the selective diffusion mask, and a wiring pattern formed on the selective diffusion mask and connected to the light emitting portion, A step of irradiating the LED array surface with light having a first wavelength having a large reflectance with respect to the selective diffusion mask to obtain a first reflected light intensity distribution on the LED array surface; And irradiating the LED array surface with light having a second wavelength whose reflectance is smaller than that of the first wavelength,
A step of obtaining a second reflected light intensity distribution on the surface of the D array and a step of obtaining a difference between the first and second reflected light intensity distributions,
The step of identifying a region having a difference in the distribution of reflected light intensity on the surface of the LED array and recognizing the reference pattern is executed.

In this method for recognizing a reference pattern of an LED array, the periphery of the selective diffusion mask formed during a photolithography process for forming an opening for the light emitting portion in the selective diffusion mask as the reference pattern. The pattern of the position detection window surrounded by is used, or the pattern of the light emitting portion is used. Furthermore, a semiconductor substrate, a selective diffusion mask made of a dielectric thin film formed on the semiconductor substrate, a light emitting portion formed on the semiconductor substrate exposed in an opening formed in the selective diffusion mask, and the selective diffusion mask. A die-bonding step for regularly arranging a plurality of LED arrays each of which has a wiring pattern formed on a diffusion mask and connected to the light-emitting portion, and a step of dice-bonding the first LED array; , Irradiating the surface of the first LED array with light having a first wavelength having a high reflectance with respect to the selective diffusion mask of the plurality of LED arrays, and performing first reflection on the surface of the first LED array. A step of obtaining a light intensity distribution, and a light of a second wavelength whose reflectance with respect to the selective diffusion mask of the plurality of LED arrays is smaller than the first wavelength, The step of irradiating the first LED array surface to obtain the second reflected light intensity distribution on the first LED array surface, and the difference between the first and second reflected light intensity distributions to obtain the first reflected light intensity distribution. Identifying a region having a difference in the distribution of reflected light intensity on the LED array surface and recognizing the first reference pattern; and irradiating the second LED array surface with the light of the first wavelength, Second LED
A step of obtaining a third reflected light intensity distribution on the array surface, and a step of irradiating the second LED array surface with light of the second wavelength to obtain a fourth reflected light intensity distribution on the second LED array surface. The step of obtaining and the difference between the third and fourth reflected light intensity distributions are obtained, a region having a difference in the reflected light intensity distributions on the surface of the second LED array is identified, and the second reference pattern is recognized. The process and the relative positions of the first and second reference patterns are detected, and the die bond position is corrected when the second LED array is die-bonded. Further, in this method for detecting the position of the LED array, as the first and second reference patterns, the periphery selected when the photolithography process of forming the opening for the light emitting portion in the selective diffusion mask is selected. The pattern of the position detecting window surrounded by the diffusion mask is used, or the pattern of the light emitting portion is used.

[0014]

The reflectance of the selective diffusion mask area formed on the surface of the LED array is largely changed with respect to the wavelength due to the interference of light because the selective diffusion mask is formed of the dielectric thin film. It has the property of On the other hand, the other wiring patterns are almost constant regardless of the wavelength, so the reflectance of the LED array surface is measured with two different wavelengths.
When the surface patterns are detected by the respective wavelengths, the two surface patterns have different surface patterns in the selective diffusion mask area portion. By taking the difference between the surface patterns of the two, the pattern of the selective diffusion mask region can be clearly discriminated.

The pattern of the position detecting window, which is formed during the photolithography process for forming the opening for the light emitting portion and is surrounded by the selective diffusion mask, can be clearly discriminated from the light emitting portion. There is no deviation in the relative positional relationship.

Further, since the light emitting portion of the LED array is surrounded by this selective diffusion mask area, the position of the pattern of the light emitting portion can be directly detected.

[0017]

EXAMPLES First, the reflectance characteristics of each part of the LED array will be described. FIG. 3 shows A- of the LED array 101 in FIG.
It is sectional drawing which showed the structure of A cross section. As mentioned above,
The LED array 101 includes a light emitting unit 104 on an N-type semiconductor substrate 106.
A selective diffusion mask 105 having an area to be formed is formed, and a P type diffusion layer 105 is formed in the N type semiconductor substrate 106 at the opening of the selective diffusion mask 105. Then, an Al wiring pattern 103 is formed on the surface of the selective diffusion mask 105 so as to be electrically connected to the P-type diffusion layer 104. FIG. 6 is a diagram showing the wavelength-reflectance characteristic of each part of the LED array 101 described above. As is clear from this figure, the Al wiring pattern
Since 103 is a metal, it has a constant reflectance for a certain range of wavelengths. Similarly, the semiconductor substrate (including the P-type diffusion layer) exposed in the opening of the selective diffusion mask 105 such as the light emitting unit 104 also has a constant reflectance for a certain range of wavelengths. However, the selective diffusion mask 105
Is formed of a dielectric thin film such as alumina or a silicon nitride film, so that the change of the reflectance with respect to the wavelength is very large due to the interference of light. The position detection of the present invention is performed by utilizing the above characteristics.

A first embodiment of the reference pattern recognition method of the present invention will be described with reference to FIG. FIG. 1A shows an LED array 201 for detecting the position by the position detecting method of the present invention.
It is the figure which showed.

This LED array 201 has basically the same structure as the conventional LED array 101, but in order to make position detection easier, an opening is provided in the selective diffusion mask 205 in addition to the light emitting section 204. The position detection window 207 is used. Since the position detection window 207 is formed by opening the selective diffusion mask 205 in the same photolithography process as the light emitting portion 204, mask misalignment such as occurs between the light emitting portion and the Al wiring pattern. The positional deviation due to the error cannot occur.

On the surface of the LED array 201, for example, as shown in FIG. 6 showing the wavelength-reflectance characteristic of each region of the LED array surface, the wavelength a having a large reflectance of the selective diffusion mask and The wavelength b with a small reflectance,
Illumination is performed with illumination light having substantially the same light intensity at the wavelength a and the wavelength b as shown in the diagram of FIG. 7 showing the wavelength-light intensity characteristics.

Regarding the selection of the wavelength a and the wavelength b at this time, since the wavelength-reflectance characteristic changes depending on the material and thickness of the dielectric thin film, it is necessary to change the conditions depending on the material and thickness of the selective diffusion mask. However, regarding the illumination light, if a conventional incandescent lamp is used, the necessary conditions are sufficiently satisfied.

At this time, CC on the surface of the LED array 201
FIG. 1B shows the reflected light intensities obtained by illuminating the cross-sectional area with the wavelength a or the wavelength b. What is shown by the dotted line is the distribution a1 of the reflected light intensity detected at the wavelength a, and what is shown by the solid line is the distribution b1 of the reflected light intensity detected at the wavelength b. Due to the wavelength-reflectance characteristic shown in FIG. 6, the reflected light intensity distribution a1 is larger than the reflected light intensity distribution b1 in the region where the selective diffusion mask 205 is present, and the light emitting portion 204
On the region, the Al wiring pattern 203 region, and the position detection window 207 region, the reflected light intensities of a1 and b1 are almost the same.

FIG. 1C shows the calculation result of the difference between the reflected light intensities of the reflected light intensity distributions a1 and b1 shown in FIG. 1B for producing the binarized image. As shown in FIG. 1C, the wavelengths a and b of the reflected light intensity distributions a1 and b1
Area where there is a difference in reflected light intensity, that is, selective diffusion mask 20
Only one part of 5 remains, the other part is mostly cancelled.

Therefore, if binarization is performed at a certain level,
The image is an image of only the selective diffusion mask area, that is, the binarized image of the first embodiment of the present invention shown in FIG.
The selective diffusion mask itself exposed on the surface is recognized as the selective diffusion mask pattern 208. Then, the area corresponding to the position detection window 207 in the selective diffusion mask pattern 208 is used as the reference pattern 208a for position correction. FIG. 10 shows the reference pattern recognition method of the present invention described above in the form of a flow chart. As shown in FIG. 10, the reference pattern recognition method of the present invention uses the first step of obtaining the difference between the image a1 and the image b1 and the calculation result obtained in the first step with a predetermined threshold value. Binarization, a1 and b1
The second step of selecting an area having a significantly different image pattern and the third step of recognizing the reference pattern from the distribution of the selected area.

Next, the position detecting method of the present invention in the die bonding process using the reference pattern of the first embodiment will be described.

First, as shown in FIG. 11A, it is assumed that the LED array 201 having the position detecting window 207 is first die-bonded. Next, as shown in FIG. 11 (b), the LED
The array 202 is die-bonded in the vicinity of the LED array 201. At this time, the LE according to the method of the first embodiment is used.
Position detection window 20 which is a reference pattern for the D arrays 201 and 202
7 is recognized as the reference pattern 208a, the relative position of the light emitting portion 204 of the LED array 202 with respect to the light emitting portion 204 of the LED array 201 is detected, and the step t and the pitch P ′ are calculated. Then, the LED array 202 is moved so that t ′ = 0 and P ′ = P, and the position is corrected and then fixed.

Of course, the step t and the pitch P'at this time
Is detected by the relative position of the position detection window 207 of the LED arrays 201 and 202, but unlike the case where the conventional aluminum wiring pattern is used, the position of the position detection window 207 with respect to the light emitting portion 204 does not change. Therefore, it can be extremely accurately determined from the predetermined relative positional relationship between the position detection window 207 and the light emitting unit 204.

By repeating the above operation, it is possible to manufacture an LED print head in which there is almost no step t ′ and the pitch P ′ between the LED arrays is substantially equal to the interval P between the light emitting portions.

The first reference pattern recognition method of the present invention is as follows.
In the embodiment, the independent position detection window 207 as the position detection reference pattern 208a is provided in the selective diffusion mask region 203, but the reference pattern identification method of the present invention is not limited to this. As shown in the binarized image of the second embodiment shown in FIG. 9, the LED array has the conventional structure,
The light emitting unit 104 itself may be used as the reference pattern 208b for position detection.

In this case, the P type diffusion layer 105 of the light emitting portion 104 and the A
Since the l wiring pattern 103 is conductive, at least a part of the outer periphery of the light emitting portion 104 is formed by the Al wiring pattern 103 (see region B in FIG. 3). The shape may change. It is necessary to pay attention to this point when the light emitting unit 104 is used as the reference pattern 208b, and in the case of FIG.
For detection of, the light emitting unit 1 on the side opposite to the Al wiring pattern 103
The boundary between 04 and the selective diffusion mask 105 (the upper part of the convex portion in the figure), and the boundary between the left and right light emitting parts 104 and the selective diffusion mask 105 (the convex portion in the figure) for detecting the pitch shift P ′. The position of the left and right side) may be used as a reference. The position detecting method in the die bond process is the same as that in the case of using the first embodiment.

Needless to say, as in the first embodiment, a position detecting window 207 serving as a reference pattern 208a and an opening serving as a light emitting portion 204 are formed in a portion independent of the Al wiring pattern 203. If it is formed in the same photolithography process as described above, a pattern having a constant shape can be used as a reference pattern for position detection regardless of the mask displacement of the Al wiring pattern 203. Therefore, the step t ′ and the pitch displacement P ′ can be detected. Is easy. Further, according to the reference pattern recognition method of the present invention, since it is possible to recognize the pattern of the light emitting portion, in addition to the position detection in the die bonding step,
It can be used to detect the position of the LED array in the dicing process. LEs formed in large quantities on semiconductor substrates
Since the position of the light emitting portion of the D array can be detected and the cut-out position can be corrected, full auto dicing of the LED array can be performed.

[0032]

As described in detail above, according to the reference pattern recognition method of the present invention, the light emitting portion itself or the position detecting window formed in the same photolithography process as the formation of the light emitting portion is used as the reference pattern. Since it is recognized, the positional relationship between the light emitting unit and the reference pattern does not change from the predetermined numerical value. Since the LED array positioning correction is performed using this reference pattern, the positional deviation of the light emitting portion between the LED arrays is extremely reduced, and it is possible to manufacture an LED print head with high printing quality. .

[Brief description of drawings]

FIG. 1 is a diagram showing an LED array used in a first embodiment of the present invention, a reflected light intensity of each part in a CC cross section of the LED array, and a calculation result for creating a binarized image. .

FIG. 2 is a diagram showing a positional relationship of LED arrays after a die bonding step.

3 is a cross-sectional structural view taken along the line AA in FIG.

FIG. 4 is a diagram showing a total reflectance distribution in the AA cross section of FIG.

FIG. 5 is a binarized image in a conventional position detection method.

FIG. 6 is a diagram showing wavelength-reflectance characteristics of respective regions of the LED array surface.

FIG. 7 is a diagram showing wavelength-light intensity characteristics of illumination light used in the present invention.

FIG. 8 is a binarized image in the position detecting method according to the first embodiment of the present invention.

FIG. 9 is a binarized image in the position detecting method according to the second embodiment of the present invention.

FIG. 10 is a flowchart of a reference pattern recognition method of the present invention.

FIG. 11 is a process drawing for explaining a die bonding process using the position detecting method of the present invention.

[Explanation of symbols] 101, 102, 202, 202 LED array 103, 203 Aluminum wiring pattern 104, 204 Light emitting part 105, 205 Selective diffusion mask 106 N-type semiconductor substrate 207 Position detection window 208 Selective diffusion mask pattern 208a, 208b Reference Pattern a1 Reflected light intensity distribution at wavelength a b1 Reflected light intensity distribution at wavelength b P Pitch of light emitting parts in the same LED array P ′ Pitch of light emitting parts between different LED arrays t ′ Step difference of light emitting parts between different LED arrays

Claims (6)

[Claims] 1. A semiconductor substrate, a selective diffusion mask made of a dielectric thin film formed on the semiconductor substrate, and a light emitting portion formed on the semiconductor substrate exposed in an opening formed in the selective diffusion mask. A wiring pattern formed on the selective diffusion mask and connected to the light emitting portion.
In the D array, a) irradiating the surface of the LED array with light of a first wavelength having a large reflectance with respect to the selective diffusion mask to obtain a first reflected light intensity distribution on the surface of the LED array. And b) irradiating the LED array surface with light having a second wavelength whose reflectance is smaller than that of the first wavelength with respect to the selective diffusion mask, and secondly reflecting light on the LED array surface. A step of obtaining an intensity distribution, and c) a step of obtaining a difference between the first and second reflected light intensity distributions, identifying an area having a difference in the reflected light intensity distribution on the LED array surface, and recognizing a reference pattern. A reference pattern recognition method for an LED array, comprising: 2. The method of recognizing a reference pattern of an LED array according to claim 1, wherein the reference pattern is a peripheral pattern formed during a photolithography process for forming an opening for the light emitting portion in the selective diffusion mask. A reference pattern recognition method for an LED array, wherein the pattern of a position detection window surrounded by a selective diffusion mask is used. 3. The reference pattern recognition method for an LED array according to claim 1, wherein the pattern of the light emitting portion is used as the reference pattern. 4. A semiconductor substrate, a selective diffusion mask made of a dielectric thin film formed on the semiconductor substrate, and a light emitting portion formed on the semiconductor substrate exposed in an opening formed in the selective diffusion mask. A die-bonding step for regularly arranging a plurality of LED arrays, each of which has a wiring pattern formed on the selective diffusion mask and connected to the light-emitting portion, a) the first LED array Dice-bonding step, and b) irradiating the surface of the first LED array with light having a first wavelength having a high reflectance with respect to the selective diffusion mask of the plurality of LED arrays, and thereby the first LED Obtaining a first reflected light intensity distribution on the array surface, and c) the reflectance of the plurality of LED arrays with respect to the selective diffusion mask is smaller than the first wavelength. Irradiating the surface of the first LED array with light having a second wavelength, and obtaining the second reflected light intensity distribution on the surface of the first LED array; and d) the first and second reflections. Obtaining a difference in light intensity distribution, identifying a region having a difference in reflected light intensity distribution on the first LED array surface, and recognizing a first reference pattern; e) second LED array surface Irradiating with the light of the first wavelength on the surface of the second LED array to obtain a third reflected light intensity distribution; and f) applying the light of the second wavelength to the surface of the second LED array. Irradiating to obtain a fourth reflected light intensity distribution on the surface of the second LED array, and g) obtaining a difference between the third and fourth reflected light intensity distributions, and reflecting on the surface of the second LED array. Identify areas with different light intensity distributions Recognizing the second reference pattern, and h) detecting the relative position of the first and second reference patterns and correcting the die bond position when the second LED array is die-bonded. A method for detecting the position of an LED array. 5. The LED array position detection method according to claim 4, wherein the first and second reference patterns are:
Position of LED array characterized by using a pattern of a position detection window surrounded by a selective diffusion mask, which is formed during a photolithography process for forming an opening for the light emitting portion in the selective diffusion mask. Detection method. 6. The LED array position detecting method according to claim 4, wherein the first and second reference patterns are:
LE using the pattern of the light emitting unit
D array position detection method.