JPH03214112A - Optical integrated circuit and package for integrated circuit - Google Patents

Abstract

PURPOSE:To easily package an optical integrated circuit into small-sized constitution with high accuracy by chucking the upper-step part of a prism and to evade damage to a prism principal part or semiconductor substrate by providing step parts on both sides of the prism. CONSTITUTION:The mutually parallel step parts 56 are formed on both sides of the prism 15 arranged on photodetectors 13 and 14. The section of the prism 15, i.e. prism section intersecting the line connecting a semiconductor laser 16 and the photodetectors 13 and 14 at right angles is in a projection shape. Consequently, the projecting upper-step part of the prism 15 is chucked to package the optical integrated circuit to small size and a chuck means contacts none of the principal part of the prism 15, photodetectors 13 and 14, and semiconductor substrate 12 where other circuit elements are formed and the damage can be evaded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to optical integrated circuits such as optical heads and composite optical elements;
The present invention also relates to integrated circuit packages that house optical integrated circuits, semiconductor integrated circuits, and the like.

[Summary of the invention]

The present invention includes a photodetector formed on a semiconductor substrate, a prism having a transflective surface disposed on the photodetector,
In an optical integrated circuit having a semiconductor laser arranged on a semiconductor substrate, by providing a stepped portion on both sides of the prism, it is possible to mount the optical integrated circuit in a small package, and the main part is not affected. (Damage due to contact, etc.)
This makes it possible to mount the optical integrated circuit device on a package by chuffing it without imparting chaffing, thereby increasing the reliability of the optical integrated circuit device.

The present invention also provides an integrated circuit package, that is, a hollow package consisting of a hollow ceramic part and a metal bottom plate that closes the bottom of the hollow ceramic part, in which the hollow ceramic part and the metal bottom plate are fused together through a brazing material whose main component is PB. This reduces stress and prevents hollow ceramic cracking and deformation due to differences in thermal expansion coefficients, and has high heat dissipation properties, making it possible to connect multiple units by forming lead frames.

[Conventional technology]

Optical heads used in optical recording and reproducing devices, such as C
Various structures have been proposed as optical heads (optical pickups) for detecting pit information on discs such as D (compact discs). 15 to 17 show an optical head previously proposed by the applicant in Japanese Patent Application No. 1-99221. In FIG. 15, (1) shows the entire optical head, and (2) shows the optical integrated circuit (3) and flexible wiring board (3) mounted on its package (5).
4), (6) and (7) are reflective mirrors, and (8) is a lens, which are attached to the case (9).
) is housed in one piece. (10) indicates an optical disc. As shown in FIGS. 16 and 17, the optical integrated circuit (3) has first and second photodiodes, such as PIN diodes, on the main surface of a semiconductor (silicon) substrate (12).
photodetectors (13) and (14) are formed, and an operating amplifier (not shown) to which signals from the photodetectors (13) and (14) are manually input is formed, and this semiconductor substrate A prism (15) having a semi-transmissive reflective surface (15a) with an angle θ = 45° is fixed to the surface including the photodetectors (13) and (14) of (12), and the semi-transmissive reflective surface of this prism (15) A silicon chip (19) with a monitor photodiode (18) formed at a position facing the surface (15a).
) with a semiconductor laser (16〉) attached, commonly known as LOP (L
(aser on Photolod) chip is fixed. This optical head (1) uses a semiconductor laser (1
The light (17) from 6) is reflected by the semi-transparent reflective surface (15a) of the prism (15), and the light (17) from the hollow package (5)
window and through hole (4a) of flexible wiring board (4)
passes through and is reflected by reflection mirrors (6) and (7),
The light is focused onto the optical disk (10) through the objective lens [8]. The returning light beam reflected from the optical disk (10) passes through the objective lens (8), reflective mirrors (7) and (6), is refracted at the semi-transparent reflective surface (15a) of the prism (15), and enters the prism (15). The light enters and is first detected by the first photodetector (13), and then reflected and detected by the second photodetector (14). The monitoring photodiode (18) detects the intensity of the laser light emitted from the semiconductor laser (16).

Note that the first and second photodetectors (13) and (14) each have a PIN diode configuration divided into three, and perform focus error detection and tracking error detection as well as detection of a reproduction signal.

On the other hand, as shown in FIGS. 12 and 13, the hollow package (5) includes a hollow ceramic part (24) consisting of three ceramic frame plates (21), (22), and (23) stacked on each other. ) and hollow ceramic part (24)
It is formed from a metal bottom plate, that is, a metal dowel pad portion (25), which is bonded so as to close the bottom surface of the metal dowel pad portion (25). The three frame-shaped plates (21>, (22> and (23)) have their frame widths dI+d2.d, respectively, a, >d2>d
s, and the third and second frame plates (23) and (22) of the upper layer form a stepped portion (27) into which the transparent lid (26) constituting the window is fitted. be done.

In addition, in the first frame-shaped plate (21) of the lower layer, the frame width d of one opposing side is the same as that of the second frame-shaped plate (22) above it.
Although the frame width d2 of the corresponding side is larger than that of the second frame plate (22), and the internal lead electrode (28) of a predetermined pattern is formed here, the frame width of the other opposing side is larger than that of the second frame plate (22). Frame width d2
is formed identically to A plurality of grooves (30) corresponding to the number of internal lead electrodes (28) are formed at equal intervals over the entire height on one opposing outer wall of the hollow ceramic part (24), and each internal lead electrode (28) ), an outer IJ electrode made of a conductive layer (for example, a metallized layer) extends inside the groove (30) along the opening side to the upper surface of the third frame plate (23). (29)
is formed. To form such a hollow package (5), as shown in FIG. 14, a hollow ceramic part (
24), are arranged and bonded together, and then the optical integrated circuits are housed, etc., to produce multiple units.Finally, the connecting portions of the lead frames (31) are cut, and multiple units are assembled at the same time. It is desired that it can be formed.

Now, in the optical integrated circuit (3), the prism (15),
Each element such as a semiconductor laser (16) is a photodiode.
pattern i.e. first and second photodetectors (13), (1
Since it is mounted based on the line (A) passing through 4), a highly accurate mounting technique is required. Especially the line (A) of the prism (15)
), that is, the angular accuracy in the rotational direction within the main surface of the substrate (12) is severe. Photodetector (13).

(14)), it is difficult to implement a single prism (15) as shown in FIG.

In order to improve the mounting accuracy of this prism (15), the present applicant previously proposed a method using a long prism in Japanese Patent Application No. 61-273393. This includes first and second photodetectors (13), (
14) On a semiconductor (silicon) wafer formed with
A long prism having a semi-transmissive reflective surface is disposed so as to span a plurality of pellets, and the semiconductor wafer is simultaneously cut using, for example, a cutter for each pellet. According to this method, since the prism is a long prism, even if there is a slight angular shift in the rotation direction, the error will be larger at the ends of the long prism, so positional accuracy at both ends of the long prism is ensured. This allows for angular accuracy. Optical integration loop (32) shown in Figure 18
is an example created using this method.

On the other hand, hollow ceramic packages for enclosing optical integrated circuits or ordinary semiconductor integrated circuits are used to improve heat dissipation of the elements (optical integrated circuits, semiconductor integrated circuits, etc.) housed in them and to improve productivity. Metal Guibond pad part (
A ceramic package with a metal bottom plate (metal bottom plate), especially a Cu-based bond pad, is required. In this case, in the above-mentioned optical integrated circuit package, the optical head (1) itself is driven via a drive system using a voice coil and a permanent magnet to perform tracking servo and focus servo, so this metal bond pad part is It needs to be non-magnetic.

Conventionally, as this type of hollow package, for example, those shown in FIGS. 9 to 11 are known. The hollow package (34) in FIG.
! Alternatively, it is constructed by bonding a bottom plate (33) made of 5iC (ceramic with good heat dissipation) or the like. (35) is a mounted element. The hollow package (36) in FIG. 10 has a Cu-based bottom plate (
38) are joined together. The Fe-based ring (37) has the effect of alleviating the strain caused by the difference in thermal expansion between the ceramic and the Cu-based ring. In the hollow package (39) in Fig. 11, a Kovar bottom plate (40) is bonded to the bottom surface of the hollow ceramic part (24), and a Cu-based plate (41) with good heat dissipation is bonded to the inner surface of this Kovar bottom plate 7 (40). It is composed of

[Problem to be solved by the invention]

Incidentally, since the optical integrated circuit (32) shown in FIG. 18 described above is manufactured using a long prism, it has the advantage of obtaining angular precision of the prism, but has the same problems as the surface method.

(1) After the long prism is arranged, it is cut into pellets together with the semiconductor wafer λ, so prisms or photodiodes (photodetectors) at both ends of the long prism are wasted (however, if the prism is too long, accuracy cannot be ensured).

(ii) When the pelletized optical integrated circuit (32) is bonded into a package, the collet (43) that chucks the pellet, that is, the optical integrated circuit (32), as shown in FIG.
) becomes large, making it difficult to integrate into a small package.

(iii) Prism (glass) in pelletizing
Since it is necessary to cut (15) and the silicon substrate (12) at the same time, it becomes difficult to set dicing conditions because materials with different properties are cut with the same blade.

Next, the hollow package shown in FIGS. 9 to 11 above (
34), (36), and (39), for example, the hollow package (34) has the disadvantage that the bottom plate material is expensive and difficult to process, and the bottom plate (33) cannot be made into a lead frame. , (39) could be made into a lead frame, but the package creation process was complicated and heat dissipation was poor. When the Cu-based lead frame is directly fused to the hollow ceramic part (24) (usually silver soldered at about 800°C),
Ceramic cracks occur during the cooling process from high temperature to room temperature during fusion, resulting in defects. Further, as shown in Fig. 8, the hollow ceramic part (24) and the Cu-based solid frame (44
), deformation (warpage) due to strain occurred from the time of fusion via the silver solder (45) (as shown in the figure) to after cooling (as shown in Figure B).

In view of the above-mentioned points, the present invention provides an optical integrated circuit that can be particularly mounted in a small package and that can avoid contact and damage to the main parts of a semiconductor substrate and prism when chucked with a collet, a bottle set, etc. It provides:

The present invention also provides an integrated circuit package that has a metal bottom plate that has good heat dissipation properties and can be formed into a lead frame, and that does not cause ceramic cracking or deformation.

[Means to solve the problem]

The present invention provides a photodetector (12) formed on a semiconductor substrate (12).
13), (14) and this photodetector (13),
(14) Transflective surface (15a) placed above
In an optical integrated circuit having a prism (15) having a semiconductor laser (15) and a semiconductor laser (16) disposed on a semiconductor substrate (12), the semiconductor laser (
16) and a photodetector (13).

(14) A pair of parallel step portions (56) are formed on both sides of the line (A>).

Further, in the integrated circuit package according to the present invention, in a hollow package consisting of a hollow ceramic part (24) and a metal bottom plate (60) that closes the bottom of the hollow ceramic part (24), the hollow ceramic part (24) and the metal Bottom plate (60
) are fused together via a brazing filler metal (61) whose main component is Pb. As the metal bottom plate (60), for example, a Cu-based bottom plate can be used, which has good heat dissipation properties and a large difference in coefficient of thermal expansion from ceramic. The brazing filler metal (61) containing Pb as a main component may contain Pb in an amount of 80% by weight or more, preferably 90% by weight or more, and impurities other than Pb include In, A, etc.
It is possible to selectively contain g, Bi, etc. Pb
If the content is less than 80% by weight, the melting point of the brazing filler metal will drop too much and the reliability of the package will be poor in subsequent thermal processes.

[Effect]

According to the optical integrated circuit described above, the photodetector (13), (1
4) Parallel step portions (56) are formed on both sides of the prism (15) disposed above, so that the cross section of the prism (15), that is, the semiconductor laser (16) and the photodetector (13),
(14) The cross section of the prism perpendicular to the line (A) connecting the lines becomes convex.

Therefore, by chucking the convex upper portion of the prism (15), it becomes possible to mount the optical integrated circuit in a small package. In addition, the stepped portion of the prism (56
) and chuck it, the prism (1
5) Main part or photodetector (photodiode) (1
3), (14) The chuck means (collet, bin set, etc.) does not come into contact with the semiconductor substrate (12) on which other circuit elements are formed, and damage caused by this is avoided.

Next, according to the above-mentioned integrated circuit package (62),
Ceramic cracking is prevented by welding the hollow ceramic part (24) and a metal bottom plate (60), such as Cu-based metal with good heat dissipation, which closes the bottom part, through a brazing material (61) mainly composed of Pb. A highly reliable package can be obtained in which the sealing performance and the strength of the fused portion are sufficient. This is because the melting point of the brazing filler metal (61) whose main component is PB is 3.
It is thought that ceramic cracking is suppressed because the temperature is low at around 00° C., so the amount of thermal strain generated is small, and the brazing filler metal (61) has a small Young's modulus and is easily plastically deformed.

〔Example〕

First, an embodiment of the optical integrated circuit according to the present invention will be described with reference to FIGS. 1 to 3, together with its manufacturing method.

In this example, as shown in FIGS. 2 and 3 (cross-sectional view taken along line A-A in FIG. 2), the area corresponding to each pellet (52) of the silicon wafer (51) is As explained in FIG.
), and after forming circuit elements such as an operational amplifier to which a signal is input, a plurality of long prisms each having a semi-transmissive reflective surface (15a), that is, in this example, a length corresponding to 4s (bellet) is formed. The shaku prism (53) is connected to the photodetector (13) and (
14) in the direction perpendicular to the line connecting (A)
It is adhered with high precision onto the silicon wafer (51) so as to cover the area corresponding to (52). In this case, the long prism (53) is formed so that its length 11 in the longitudinal direction is slightly shorter (L>l1l) than the length 12 of the silicon wafer (51) (4 bezels) (52).

Although not shown, a silicon chip (19) on which a semiconductor laser (16) shown in FIG. 16 is mounted can be bonded to a region corresponding to each pellet.

Next, the scribe line (S) of each element (pellet) is
), cut only the elongated prism (53) to the middle of the thickness indicated by the chain line (54) (so-called half-cut). The blade width is set to a width d that can sufficiently cover 11Jj (55) between the joint portions of adjacent long prisms (53)M. Next, a thin blade for both silicon and glass (
The remaining thickness of the prism (53) and the entire silicon wafer (51) are cut (so-called full cut) along the scribe line (S) using a blade specifically designed for silicon (a blade specifically designed for silicon is acceptable) and pelletized. In this way, the first and second photodetectors (for example
A semiconductor laser (16) is placed on a silicon chip (Step 9) on which a monitor photodiode (18) is formed, on a predetermined area of the semiconductor substrate 12) on which 13) and (14), etc. are formed.
) is glued to the LOP chip, and '! J1 and the second photodetector (13) and (14) have a transflective surface (15a) on the surface thereof, and a semiconductor laser (16)
and a photodetector (13).

A target optical integrated circuit (57) is obtained by bonding prisms (15) having mutually parallel step portions (5G) on both sides of the line (A) connecting (14).

According to the optical integrated circuit (57) described above, the elongated prism (5
By using 3), the prism (15) is mounted on each pellet with high precision. At the same time, parallel step portions (56) are provided on both sides of the prism (15) except for the main portion, so as shown in FIG. By chucking the collet (43) etc., the size of the collet (43) etc. can be kept small, making it possible to mount the optical integrated circuit (57) in a small package. Also prism (15)
Since the upper stage part has high precision, it is possible to improve the assembly precision.

When chucking the optical integrated circuit (57), the step part (56) of the prism (15) is brought into contact with the chuck as shown in FIG. cholera) (43), etc., do not come into direct contact with each other, and therefore damage caused by contact can be avoided.

Furthermore, optical integration times! 8 (57), the length l of the long 7' rhythm (53) is set on a silicon wafer (57).
Slightly shorter than the length 12 for 4 bullets in 1),
After gluing the long prisms (53) for each bullet, the long prisms (53) are moved halfway along the scribe line (S) using a thick blade that includes gaps (55) between adjacent long prisms (53). Since the remaining thickness of the long prism and the silicon wafer (51) are cut at the same time, the shape and size of the pellets are almost the same at both ends of the long prism (53), and all It can be used effectively, eliminating waste of prisms and photodetectors (photodiodes). In addition, dicing is performed in two stages: half-cutting with a blade specifically designed for prisms (glass), and full-cutting using blades that can be used for both glass and silicon, making it easy to set dicing conditions.
The frequency of cracking and chipping of the semiconductor substrate (12) on which the photodetectors (13) and (14) are formed is reduced, and this type of optical integrated circuit (57) can be manufactured with high yield.

The upper part shows the case where a long prism (53) is used, but if a prism mounter that can secure sufficient mounting accuracy of the prism (15) is used, the stepped part ( It is also possible to independently mount the prism (15) with 56). Also in such an optical integrated circuit (58), by having the stepped portion (56) on the prism (15), it is possible to chuck the main part of the prism and the semiconductor substrate (12) without damaging the optical integrated circuit (58). 58) can be mounted in a small package.

Next, FIG. 7 shows an embodiment of an integrated circuit package according to the present invention that houses the above-mentioned optical integrated circuit or semiconductor integrated circuit. Although the hollow ceramic portion is shown in a simplified manner in FIG. 7, it can have the same configuration as in FIGS. 12 and 13.

In this example, a Cu-based lead frame (600 ) are fused using a brazing filler metal (61) whose main component is Pb (lead), and then the connecting portion of the lead frame (60) is cut to form an integrated circuit package (62). (35) is par/'T-
This is an element such as an optical integrated circuit or a semiconductor integrated circuit that is bonded into the chip (62). The brazing filler metal (61) containing Pb as a main component may contain 80% by weight or more of Pb, preferably 90% by weight or more, and may contain In, Ag as impurities.
, Bi, etc. can be selectively included. When pb is less than 80% by weight, the melting point becomes too low and reliability as a package decreases. In this example, Pb-
In-Ag-based (Pb: 92.5% by weight, In+5% by weight, Heg: 2.5% by weight) low-temperature brazing filler metal (melting point 307%)
℃) was used.

According to the package (62) having such a configuration, the hollow ceramic portion (24) and the Cu-based lead frame (60) are
By fusing through the b-In-Ag brazing material (61), there is no ceramic cracking, and sealing performance is improved.
The strength of the fused portion was also sufficient, and furthermore, no deformation such as warping due to a difference in thermal expansion coefficient occurred.

The reason for this is that the melting point of the Pb-In-Ag brazing filler metal (61) is as low as approximately 300°C, so the amount of thermal strain generated is small;
It is thought that ceramic cracking is suppressed because the brazing filler metal (61) has a small Young's modulus and is easily plastically deformed.

The effectiveness of the latter Young's modulus and plastic deformation can be understood from the fact that ceramic cracking occurred when ^υSn brazing filler metal (melting point 232°C), which has a lower melting point, was used.

Table 1 shows the physical property constants of related materials.

Thermal strain can be explained to some extent theoretically, and the above experimental facts can also be explained, for example, by stain corrosion using a two-dimensional finite element method using a simplified model. Assuming that the critical stress of ceramic is 30 Kg/+nm, the maximum stress was calculated to be approximately 27 Kg/lT1m for the AuSn-based brazing material, and 21 Kg/mm for the PB-based brazing material.

It can be designed to be sufficiently safe if stress relaxation due to the softness of the Pb brazing filler metal is considered.

As mentioned above, by using the low melting point, low stress brazing filler metal (61) mainly composed of PB, the hollow ceramic part (2
4) and the Cu-based lead frame (60) can be easily fused together, making it an integrated product that is inexpensive, has great heat dissipation, can be connected in multiple lead frames, and is non-magnetic. A package for circuits, in particular for the above-mentioned optical integrated circuits, is obtained.

〔Effect of the invention〕

According to the optical integrated circuit of the present invention, since the prism is configured with stepped portions on both sides, the optical integrated circuit can be mounted in a small package with high accuracy and easily by chucking the upper part of the prism. It becomes possible. At the same time, since the prism is chucked against the stepped part, damage to the main part of the prism or the semiconductor substrate can be avoided.
A highly reliable optical integrated circuit can be provided.

According to the package for the integrated circuit of the present invention, in a hollow ceramic and a metal bottom plate that blocks the bottom, a low -melting point with a hollow ceramic part and a metal bottom plate that blocks its bottom as a PB. , Ceramic cracking by fusion through low stress brazing filler metal,
Deformation etc. can be prevented. Therefore, it is possible to use ceramics and a Cu-based metal bottom plate with a high coefficient of thermal expansion, for example, and a package that has high heat dissipation, can be connected in multiple units using a lead frame, and is non-magnetic and inexpensive. This is particularly suitable for use in packages for optical integrated circuits.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the optical integrated circuit of the present invention, and FIG.
The figure is a perspective view showing an example of the manufacturing method, and Figure 3 is A-A in Figure 2.
4 is a perspective view showing another example of the optical integrated circuit of the present invention, FIG. 5 is a sectional view of the optical integrated circuit according to the present invention chucked with a collet, and FIG. 6 is a linear sectional view. 7 is a cross-sectional view of a conventional optical integrated circuit chucked with a collet.
The figure is a configuration diagram showing an example of an integrated circuit package according to the present invention, No. 8 vg! JA and B are configuration diagrams of a conventional package for explanation, FIGS. 9 to 11 are configuration diagrams showing examples of conventional packages, and FIGS. 12 and 13 are perspective views of an optical integrated circuit package and its 14 is a plan view of the manufacturing process of the package, FIG. 15 is a sectional view showing an example of an optical head, FIGS. 16 and 17 are perspective views and side views of the optical integrated circuit, and FIG. FIG. 18 is a perspective view showing another example of a conventional optical integrated circuit. (12) is a semiconductor substrate, (13) and (14) are photodetectors, (15) is a prism, (16) is a semiconductor laser, (56) is a stepped portion, (24) is a hollow ceramic portion, (
, 60) is a Cu-based lead frame, and (61) is a brazing filler metal whose main component is PB. Thursday All Days and Months 1; I Run Thousand Yakki Sokpa's Ifegohesire]
5th section 5 Nayawo kink of the result of the ``: 1 shaku rebuke Figure 6 z6* (struggle conventional 0 bar, 7 cage structure 1η Figure 35 Traditional noggoji structure △ 1 Figure 11 ■ Figure 13 4 beauty openings of conventional bar/I cage

Claims (1)

[Claims] 1. A light beam comprising a photodetector formed on a semiconductor substrate, a prism having a transflective surface disposed on the photodetector, and a semiconductor laser disposed on the semiconductor substrate. An optical integrated circuit comprising: a stepped portion on both sides of the prism; 2. In a hollow package consisting of a hollow ceramic part and a metal bottom plate that closes the bottom of the hollow ceramic part, an integrated circuit in which the hollow ceramic part and the metal bottom plate are fused together via a brazing material whose main component is Pb. package for.