JPH03171657A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enable heat released from a polycrystalline semiconductor resistor to be effectively dissipated so as to effectively prevent a hot spot from being generated by a method wherein a heat dissipating means is provided to the polycrystalline semiconductor resistor. CONSTITUTION:The ends of a polysilicon resistor 1 are brought into ohmic contact with a metal wiring 3 of Al or the like through contact windows 4 respectively. A conductive protrusion 2 is provided to a part of the resistor 1. The protrusion 2 is conductive and higher than a surrounding insulator in thermal conductivity. Joule heat released from the resistor 1 is dissipated through the intermediary of the protrusion 2. A protrusion serving as a heat radiator is properly provided, whereby a part of the resistor 1 where a current flows is prevented from being heated, and a hot spot is restrained from occurring.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor device using a polycrystalline semiconductor, such as polysilicon, as an electrical resistor, in a semiconductor device using polysilicon as an electrical resistor, there is A semiconductor substrate, a first insulating film formed on the semiconductor substrate, a polycrystalline semiconductor resistor formed on the insulating film and defining a current path connected between a pair of t-poles;
and a second insulating film formed on the polycrystalline semiconductor resistor, and the polycrystalline semiconductor resistor is formed so as to have a protrusion for loosening at its l portion. [Industrial Application Field] The present invention relates to a semiconductor device, and particularly to a semiconductor device using a polycrystalline semiconductor, such as polysilicon, as an electrical resistor. In this specification, the term "polycrystalline semiconductor" refers to a concept in contrast to single-crystalline semiconductors, and includes so-called "amorphous semiconductors." [Prior Art J] In the manufacture of semiconductor integrated circuit v8 devices, resistance elements are formed in a silicon substrate using an impurity diffusion process. For example, a p-type stripe region is diffused into an n-type semiconductor layer, and a pair of metal electrodes are connected to both ends of the p-type stripe region. pntH between the n-type semiconductor layer and the p-type stripe region
biasing the n-type semiconductor layer so as to reverse bias the
When a current is caused to flow between a pair of metal t-poles, the p-type stripe region can be used as a resistance element having a nearly constant resistance value. Joule heat is generated in a resistive element when current flows through it. The bulk diffused resistor as described above is surrounded by silicon with high thermal conductivity, so the generated heat is transferred to the surrounding bulk silicon and radiated. For this reason, heat generation from the resistive element did not pose a particular problem. Incidentally, as the degree of integration of semiconductor integrated circuit devices improves, the density of integrated circuits increases. For this reason, it is desired that the active and passive elements that make up the circuit become smaller and smaller. It is also desired that resistive elements be made smaller and have higher resistance. In recent years, the use of resistors using polycrystalline silicon (polysilicon) has been progressing. Polysilicon can be formed on a substrate, increasing the area utilization of the substrate. For example, a steel structure called ESPER and its process were developed. In this structure, the emitter lead electrode and base lead electrode are formed from polysilicon, which is a polycrystalline semiconductor. This polysilicon process can simultaneously form a resistor. A high-resistance polysilicon resistor is formed at the same time as the emitter (or base) extraction electrode, and used as a load resistor. By using polycrystals, high resistivity regions can be formed,
Since the surrounding area is covered with an oxide film, etc., isolation using a pn junction such as a diffused resistor is not required. As described above, polysilicon resistors have the advantage of being suitable for miniaturization, and from the viewpoint of high density, polysilicon resistors are increasingly being used. [Problem to be Solved by the Invention 1] However, since the polysilicon resistor is formed on a silicon oxide film that has poor heat conductivity, hot spots, which are localized high-temperature areas, occur due to the resistor's completeness. This hot spot excessively heats the upper layer wiring, such as the ^1 wiring, which is wired above the resistor via an insulating layer, making it easy to cause disconnection of the ^1 wiring due to electromigration. This shortens the lifespan of semiconductor devices and reduces reliability. Furthermore, the rise in temperature of the resistor due to hot spots causes fluctuations in the resistance value of the resistor itself. Generally speaking, the resistance value of a semiconductor resistor decreases as the temperature rises, and as the temperature decreases, the resistance value increases and returns to its original value. However, if the temperature becomes too high, the resistance value will not return to its original value (generally becomes higher) even when the temperature drops, causing a change in resistance value over time. These phenomena are undesirable because they cause a decrease in the reliability of manufactured semiconductor devices. Electromigration will be specifically explained below with reference to the drawings. FIG. 7(A) is a plan view of a semiconductor device using a conventional polysilicon resistor, and FIG. 7(B) is a plan view of a semiconductor device using a conventional polysilicon resistor.
A sectional view taken along line II-II' of A) is shown. In FIG. 7, both ends of a polysilicon resistor 71 are in ohmic contact with metal wiring (^1) 73 through contact windows 74. Another ^1 wiring 76 is formed on the silicon oxide insulating layer 79 above the resistor 7l so as to intersect with the polysilicon resistor 71. Upper and lower layers 78, 7 of the resistor 71
Since 9 is a silicon oxide layer, heat conduction is poor, and resistor 7
1 forms a hot spot when heated by Joule ripening. Eventually, the heat heats the A1 wiring 76 at the top. When a current flows through the matured A1 wiring 76, electromigration occurs, and the 8lt pole 76 gradually becomes thinner and eventually becomes disconnected as shown in FIG.
Similarly, electromigration occurs even when the A1 wiring is 76° without the 76 wiring. The purpose of the present invention is to solve the problems of electromigration of metal wiring due to hot spots or changes in the resistance value of the resistor in semiconductor devices that use polycrystalline semiconductors, particularly polysilicon, as electrical resistors, and to provide highly reliable semiconductor devices. The purpose is to provide equipment. [Means for Solving the Problems] According to the present invention, a ripening means is provided in a polycrystalline semiconductor resistance element formed on a semiconductor substrate. Figure 1 is a diagram explaining the principle of the present invention. Both ends of the polysilicon resistor 1 are in ohmic contact with a metal wiring 3 such as ^1 through a contact window 4. The resistor 1 is shaped by providing a conductive protrusion 2 on one part thereof. Note that FIG. 1(B) shows a cross-sectional view taken along line II' in FIG. 1(A). An oxide film 8 is formed on a semiconductor substrate 7 made of Si or the like, and a resistor 1 made of polysilicon is formed thereon. Both ends of the polysilicon resistor 1 are in ohmic contact with a wiring layer 3 such as ^1. An insulating film 9 is formed to cover these conductors 1 and 3. Other wiring lines 6 and 6° are formed on the insulating film 9. [Function] The protrusion 2 is birch conductive and has a higher electrical strength than the surrounding insulators. The Joule ripening generated in the resistor 1 is released through this protrusion 2. By appropriately providing the projections that serve as heat radiators, the portions of the resistor 1 through which current flows are prevented from ripening, and the generation of hot spots is prevented. The dimensions, shape, and area of the protrusion 2 are adjusted as appropriate depending on the amount of heat dissipation required for each semiconductor device. While adopting an elliptical structure using polycrystalline semiconductor resistive elements that is advantageous for high density, it prevents hot spots from occurring in the polycrystalline semiconductor resistive elements and prevents disconnection of metal wiring due to electromigration and damage to resistors. Changes in resistance can be prevented. [Examples] Examples of the present invention will be described below with reference to the drawings. In the drawings of the actual knee example shown below, the upper layer ^1 wiring 6, 6° shown in Fig. 1(B) is omitted for the sake of simplification of the drawings. FIG. 2 is a plan view showing the top of a semiconductor device according to an embodiment of the present invention. Its cross-sectional structure is similar to that in Figure 1 (B). It can be manufactured using the same manufacturing process as conventional technology. A silicon oxide layer is formed on the substrate by thermally oxidizing the surface of the silicon substrate, and then thermal decomposition CVD,
A polysilicon layer is formed by plasma CVD or the like. A polysilicon resistor 21 is patterned from this polysilicon layer. At this time, the protrusion 22 protruding from the polysilicon resistor 21 is also patterned. An insulating film is formed on the polysilicon resistor 21, and contact windows are opened in the insulation at both ends of the polysilicon resistor 21.
A wiring layer 23 such as A1 is formed on this layer and patterned. Both ends of the polysilicon resistor 21 are in ohmic contact with the ^1 metal wiring 23 through contact windows 24. The polysilicon resistor 21 is patterned with protrusions 22 provided on the sides of the middle part (where current flows) sandwiched by the contact windows 24. Since the projection 22 is connected to the current path only at one end and protrudes while the other end remains floating, it does not substantially function as a current path (resistance). However, since it is physically and thermally continuous, it acts as a heat dissipator against the growth in the polysilicon resistor 21 and prevents the occurrence of hot spots in the polysilicon resistor 21. Note that the length Q and width W of the polysilicon resistor 21 vary depending on the resistance value, etc., but for example, e=10"-20 μm,
w=2μm. The width S of the protrusion 22 is, for example, about 1
~2 μm, and the wide part at the tip is several μm square. Note that an extended and enlarged protrusion 25 is shown extending from the left contact window 24 to the left and continuing to the polysilicon resistor 21. This protrusion 25 is also connected to the current path only through 1r4, and the other end is in a floating state, so it does not substantially contribute as a current conductor, but functions as a heat sink similar to the protrusion 22. Although FIG. 2 shows an example in which both protrusions 22 and 25 of the polysilicon resistor serving as a heat sink are formed, only one of the protrusions 22 and 25 may be formed, or both heat sinks may be formed as shown in the figure. You can also express it. However, in the case of only the protrusion 25, the thermal resistance tends to be high because it is located away from the Joule heat generation area. The heat dissipation area is the protrusion 22
It is desirable to make it wider than in the case of . FIG. 3 shows the structure of a semiconductor device according to another embodiment of the present invention. In this embodiment, for example, two polysilicon resistors 31 are connected to the ^1 metal wiring 36 connected to the power supply VCC.
This is an elliptical structure that supplies voltage to the A1 metal wirings 33a and 33b through the A1 metal wiring lines 33a and 33b. Polysilicon resistor 31a, 3
lb is continuous with the polysilicon common portion 32 which becomes the protrusion. The metal wiring 36 is in ohmic contact with the polysilicon common portion 32 via the contact window 35. The polysilicon common portion 32 is connected to the band-shaped regions 31a and 3lb for forming electrical resistance, and is formed sufficiently wide to provide sufficient heat dissipation. In FIG. 3, one polysilicon common portion 32 is divided into two strip regions 31a and 3lb.
However, more strip-shaped areas may be connected in parallel. The contact window 35 is connected to each strip area 31a, 3l.
It may be placed sufficiently close to b, and it may be one window area that is elongated in the vertical direction in the figure. If sufficient heat dissipation performance cannot be obtained with the common portion 32 alone, as shown in FIG.
A protrusion may be formed in the middle part of 1a or 3lb to promote heat dissipation. FIGS. 4A, 4B, and 4C each show the structure of a polysilicon resistor portion of a semiconductor device according to still another embodiment of the present invention. Both have an elliptical shape with multiple protrusions formed on the sides of the middle part of the polysilicon resistor to form a heat sink. In the case shown in FIG. 4A, heat dissipation protrusions 42a and 42b are formed at both ends of the polysilicon resistor 41 at the same location. For example, it may be made to protrude from the center of the polysilicon resistor 41 to both sides. The one shown in FIG. 4(B) has protrusions 42a and 42b for heat dissipation on one side of the polysilicon resistor 41.
is formed. This can be used when there is another structure on one side and it is difficult to create a protrusion for heat dissipation. Figure 4 (C
), heat radiation protrusions 42a to 42e are formed alternately on both sides of a polysilicon resistor 41. This can be used when it is desired to provide the ripening means as evenly as possible along the length of the polysilicon resistor. All of the semiconductor devices with the structure described above can be manufactured using conventional manufacturing methods, except for changing the patterning pattern of the polysilicon resistor. Next, FIG. 2 shows still another embodiment of the semiconductor device of the present invention. The polysilicon resistor 5l has metal wiring 5 at both ends.
3 and the contact window 54 make ohmic contact.
Furthermore, metal dummy electrodes 52a, 52b are formed on the intermediate portion of polysilicon resistor 51 and are contacted with resistor 51 at contact windows 55a, 55b. These dummy T-poles 52a and 52b are formed by forming a polysilicon resistor 5l on a silicon oxide layer, and then forming a silicon oxide film, and when opening a contact window 54 in this silicon oxide film, contact windows 55a and 55b are also opened. However, the dummy electrodes 52a and 52b can be formed by patterning at the same time as the process of forming the A1 metal layer and forming the metal wiring 53. Since the dummy electrodes 52a and 52b are in contact with the polysilicon resistor 51 only at a distance of 1 m, they do not act as current paths, but act as heat sinks through thermal contact, thereby preventing the generation of hot spots in the resistor 51. To prevent.
The number and size of tummy electrodes are determined by considering the required amount of heat dissipation. Note that it is also possible to omit the contact window 55a, although heat conduction will be reduced. FIGS. 6(A) and 6(B) show still another embodiment of the semiconductor device of the present invention. This will be explained using a cross-sectional view along the length of a polysilicon resistor similar to FIG. 1(B). In the embodiment shown in FIG. 6, instead of providing a heat dissipation body for the polysilicon resistor 61, the polysilicon resistor 61 itself is placed close to a silicon substrate with very good thermal conductivity as a heat dissipation means to dissipate heat. be. In FIG. 6 (A>), a silicon oxide layer 68 is formed on a silicon substrate 67 by thermal oxidation or the like. A part of the rli silicon layer 68 is selectively etched, and then a thin oxide film is formed. The silicon oxide layer 68
Make the thickness of some parts thinner than others. Further, a polysilicon resistor 61 is formed on the silicon oxide layer 68 and covered with an insulating film 69. After opening the contact window, a metal wiring 63 and other wiring 66 that make ohmic contact with the polysilicon resistor 61 are formed by sputtering or the like, and after patterning, an insulating layer 69 such as PSG is formed.
Cover with °. Furthermore, another metal wiring 66° is formed on top of that. Therefore, the polysilicon resistor 61 approaches the silicon substrate 67 through the thin portion of the silicon oxide layer 68. Since the thermal resistance between the resistor 61 and the silicon substrate 67 is low, heat generated in the polysilicon resistor 6l in the thin portion of the silicon oxide layer 68 is easily radiated to the silicon substrate 67. As a result, the occurrence of hot spots is prevented. The embodiment of FIG. 6(B) is basically manufactured in the same manner as that of FIG. 6(A), but in FIG. 6(B), a part of the silicon oxide layer 68 on the silicon substrate 67 is manufactured. is completely removed to expose the silicon substrate 67. Therefore, heat radiation from the polysilicon resistor 61 to the substrate 67 is further improved. However, the contact portion of the substrate 67 that comes into contact with the polysilicon resistor 61 is designed to be an area where contact will not cause any problem in terms of the functionality of the semiconductor device. For example, the contact portion may be an electrically floating region, such as a pn junction or an isolation region electrically separated by a dielectric region. Although the present invention has been described above with reference to Examples, the present invention is not limited thereto. For example, it will be obvious to those skilled in the art that various improvements, changes, combinations, etc. are possible. For example, using a metal other than A1 as the metal wiring, dummy electrodes. using a polysilicon region as
It will be obvious to those skilled in the art that it is possible to form a polysilicon resistor on top of metal wiring. [Effects of the Invention] As explained above, according to the present invention, heat generated in the polycrystalline semiconductor resistor is effectively radiated by providing the heat radiation means in the polycrystalline semiconductor resistor. Therefore, the occurrence of hot spots can be effectively prevented. By preventing the occurrence of hot spots, it is possible to prevent changes in wiring over time or changes in the resistance value of resistors over time due to electromigration. It is possible to provide a semiconductor device that is easy to downsize and has high reliability.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are diagrams explaining the principle of the present invention, Figure 1 (A> is a plan view, Figure 1 (B) is a sectional view, and Figure 2 is an embodiment of the present invention FIG. 3 is a plan view showing the structure of a semiconductor device according to another embodiment of the present invention, and FIGS. 4(A) to (C) are according to still another embodiment of the present invention. FIG. 5 is a plan view showing a horizontal structure of a semiconductor device according to still another embodiment of the present invention, and FIGS. FIGS. 7A and 7B are cross-sectional views showing the top of the semiconductor device according to the embodiment.
) are a plan view and a cross-sectional view showing the elliptical structure of a semiconductor device according to the conventional technology, and Figure 8 is a diagram showing a state in which the metal wiring above the polysilicon resistor of the semiconductor device according to the conventional technology is disconnected. In the figure: 1, 21.31a, 71 2 22, 25, 3, 23. 73 4 74 6. 6゜24, 3lb. 41. 51, polysilicon resistor 32.42a-42e polysilicon protrusion 33a, 33b, 36, 53.63 metal wiring or electrode 34a. ．． 34b, 35, 54, 55, contact window 66, 66° 76.76' Other wiring semiconductor substrate oxide film insulating film dummy t-pole 6 1 , (A) Plan view (B) Cross-sectional view Fig. 1 Semiconductor according to the embodiment 54.55: Semiconductor device according to the contact window embodiment FIG. 5 (B) Part 2 FIG. 6

Claims (1)

[Scope of Claims] (1) A semiconductor substrate (7), a first insulating film (8) formed on the semiconductor substrate, and a pair of insulating films formed on the insulating film (8). A polycrystalline semiconductor resistor (
1), and a second insulating film (9) formed on the polycrystalline semiconductor resistor (1), and the polycrystalline semiconductor resistor (1) has a heat dissipation layer in a part thereof. A semiconductor device provided with a protrusion (2). (2) The protrusion (2) is made of the same material as the resistor (1) and is formed integrally with the resistor, and only one end thereof has a polycrystalline semiconductor region electrically connected to the current path. 2. The semiconductor device according to claim 1. (3), the protrusion (2) is the polycrystalline semiconductor resistor (
2. The semiconductor device according to claim 1, wherein the semiconductor device includes a metal region that is in contact with one of the points in step 1) and is insulated from other parts than the contact portion. (4) a semiconductor substrate (67); a first insulating film (68) formed on the semiconductor substrate (67); and a pair of wiring lines (63) formed on the insulating film (68).
), and a second polycrystalline semiconductor resistor (61) formed on the polycrystalline semiconductor resistor (61).
an insulating film (69), wherein a portion of the polycrystalline semiconductor resistor (61) is closer to the semiconductor substrate (67) than other portions. (5) The first insulating film (68) has a portion that is thinner than other portions, and the polycrystalline semiconductor resistor (61) is formed on the thin portion. The semiconductor device described. (6) A portion of the first insulating film (68) is removed to expose the semiconductor substrate (67), and a portion of the polycrystalline semiconductor resistor (61) is removed from the exposed semiconductor substrate (67). )
5. The semiconductor device according to claim 4, wherein the semiconductor device is formed in contact with.