JPS62112337A - Inspection of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the heating distribution to be inspected accurately and efficiently by a method wherein infrared rays are used jointly to inspect the heating distribution on the surface of a semiconductor device using liquid crystal. CONSTITUTION:A semiconductor device 1 is thinly and evenly coated with liquid crystal 2. The device 1 driven by a driving circuit 3 is supplied with specified power supply voltage, input signal and output load. Besides, a thermostatic oven 4 shuts off any external temperature fluctuation to maintain the ambient temperature of device 1 constant. In the thermostatic oven 4, an infrared ray source 5 emits even infrared rays to heat the surface of semiconductor device 1 and the liquid crystal 2 evenly while an infrared ray beam source 6 emits finely throttled infrared ray beams to heat any one liquid crystal on the point. Finally a beam controller 7 controls the infrared ray beams to scan the surface of semiconductor device 1 while an optical microscope 8 observes any optical change of liquid crystal. Through these procedures, the results of observation can be stored in an image memory 9 to be converted into a heating distribution chart by an image processor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of testing a semiconductor device, and more particularly to a method of testing heat distribution on the surface of a semiconductor device.

〔overview〕

The present invention provides a method for inspecting a semiconductor device in which the surface of the semiconductor device is uniformly coated with liquid crystal and the optical characteristics of the liquid crystal change at a specific temperature to inspect the heat distribution on the surface of the semiconductor device. By performing the inspection while irradiating the surface of the device with infrared rays, it is possible to accurately, efficiently and economically inspect the heat distribution on the surface of the semiconductor device.

[Conventional technology]

Conventionally, this type of inspection method involves uniformly coating the surface of a semiconductor device with liquid crystal whose optical properties change at a specific temperature.
The semiconductor device is placed in a thermostatic chamber kept at a temperature lower than the temperature at which the optical characteristics of the liquid crystal change, and the semiconductor device is operated by connecting a predetermined power supply voltage, input signal, and output load. This has been a method of inspecting the heat generation distribution on the surface of a semiconductor device by observing the surface of the semiconductor device and determining areas where the optical characteristics of the liquid crystal have changed.

[Problem that the invention seeks to solve]

In the conventional semiconductor device inspection method described above, the heat generation distribution on the surface of the semiconductor device is compared with the difference between the temperature at which the optical characteristics of the liquid crystal change and the temperature of the constant temperature oven, and the temperature rise due to the heat generation of the semiconductor device. In order to determine the distribution of heat generation on the surface of a semiconductor device, it was necessary to use multiple types of liquid crystals with different temperatures at which their optical properties change, or to vary the temperature of the thermostat. . However, using multiple types of liquid crystals is inefficient because the liquid crystal must be removed from the surface of the semiconductor device and reapplied, and it is uneconomical because multiple types of expensive liquid crystals are required. Second, it is not possible to continuously determine the heat distribution even if many types of liquid crystals are used.Secondly, if you do not place the semiconductor device in a constant temperature oven and wait until the temperature stabilizes every time you replace the liquid crystal. There were drawbacks such as inefficiency and inefficiency.

Furthermore, changing the temperature of the thermostatic oven has the drawback of being inefficient because it is necessary to wait until the temperature inside the thermostatic oven stabilizes each time the temperature setting of the thermostatic oven is changed. Another method is to observe changes in the liquid crystal while gradually changing the temperature of the thermostatic oven, but due to heat conduction from the wiring for driving the semiconductor device and their heat capacity, There was a drawback that the set temperature was transmitted unevenly, making it impossible to accurately inspect the heat distribution.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for testing a semiconductor device that can accurately, efficiently, and economically test the heat distribution on the surface of a semiconductor device by eliminating the above-mentioned drawbacks.

[Means for solving problems]

The semiconductor device inspection method of the present invention involves uniformly applying liquid crystal to the surface of the semiconductor device, and inspecting the heat generation distribution on the surface of the semiconductor device by utilizing the fact that the optical characteristics of the liquid crystal change at a specific temperature. The device inspection method is characterized in that the heat generation distribution is inspected while irradiating the surface of the semiconductor device with infrared rays.

Further, in the semiconductor device inspection method of the present invention, it is preferable that the surface to be measured is uniformly irradiated with infrared rays.

Further, in the semiconductor device inspection method of the present invention, it is preferable that the infrared rays be focused into a narrow beam and irradiated while scanning.

Furthermore, in the method for inspecting a semiconductor device of the present invention, it is preferable that infrared rays be irradiated in a narrow beam-like manner in a pulsed manner.

[For production]

The present invention makes it possible to uniformly and quickly apply heat to the surface of a semiconductor device by uniformly irradiating the surface of the semiconductor device with, for example, infrared rays instead of changing the temperature setting of a thermostatic oven. The heat distribution on the surface of the device can be obtained.

Further, the present invention irradiates the surface of an operating semiconductor device with a narrow beam of infrared light, such as infrared laser light,
The infrared beam is scanned over the surface of the semiconductor device while measuring the area of the region where the optical properties of the liquid crystal have changed around the infrared irradiation point. Since the area of the region where the optical properties of the liquid crystal have changed is proportional to the amount of heat generated at the irradiation point, it is possible to obtain the heat generation distribution on the surface of the semiconductor device with one scan of infrared rays.

Furthermore, the present invention irradiates the surface of an operating semiconductor device with infrared rays narrowly focused into a beam in a pulsed manner, and detects the area of the region where the optical characteristics of the liquid crystal have changed around the irradiation point of the infrared beam pulse, or An infrared beam pulse is scanned over the surface of the semiconductor device while measuring the rate at which its area increases. Since the area of the region where the optical properties of the liquid crystal have changed and the rate at which the area increases are proportional to the amount of heat generated at the irradiation point, it is possible to obtain the heat generation distribution on the surface of the semiconductor device with one scan of the infrared beam. can.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an inspection apparatus for carrying out the method of the present invention. A thin and uniform liquid crystal 2 is placed on the semiconductor device 1.
is coated. The drive circuit 3 applies a predetermined power supply voltage, input signal, and output load to the semiconductor device 1 to operate the semiconductor device 1. The thermostat 4 blocks external temperature fluctuations that may cause errors in the measurement of heat generation distribution, and keeps the ambient temperature of the semiconductor device 1 constant. The infrared light source 5 generates uniform infrared light to uniformly heat the surface of the semiconductor device W1 and the liquid crystal 2. The infrared beam light source 6 generates a narrow infrared beam for applying heat to one point on the surface of the semiconductor device 1 and the liquid crystal 2 at that point.

The beam control unit 7 controls the infrared beam to be emitted continuously or in a pulsed manner. The beam control unit 7 also controls the infrared beam to scan the surface of the semiconductor device 1 . The optical microscope 8 is used to observe changes in the optical characteristics of the liquid crystal, and the observation results are stored as images in an image storage device 9 and converted into a heat generation distribution diagram by an image processing device 10.

FIG. 2 is a schematic diagram of an example of the observation results of the optical characteristics of the liquid crystal 2 obtained by uniformly irradiating infrared rays from the infrared light source 5 in FIG. 1. Figure 2 shows the elapsed time from the start of uniform infrared ray irradiation in the order of (al, (1)), and (C).Liquid crystal specific change area 1) where the optical characteristics of the liquid crystal changed due to heat generation.
is indicated by diagonal lines. Immediately after starting to irradiate infrared rays,
The amount of heat that the liquid crystal receives from infrared rays is still small, so the second
As shown in Figure (a), only the optical characteristics of the liquid crystal in the portion where the amount of heat generated is particularly large is changed. That is, Fig. 2 (a
) indicates that heat generation is particularly high in the shaded area.

If the infrared rays are further uniformly irradiated, the amount of heat that the liquid crystal receives from the infrared rays will increase, as shown in Figure 2 (tb).
Next, the optical properties of the liquid crystal in areas that generate a lot of heat change. When uniform infrared rays are further irradiated, the optical characteristics of the liquid crystal in most regions change, as shown in FIG. 2 (ic). In FIG. 2(C), the area without diagonal lines means an area where almost no heat is generated.

Each of these three images is given a different color, and the image processing device 10
By overlapping them, a heat distribution map can be obtained.

FIG. 3 shows the observed results of changes in the optical characteristics of the liquid crystal 2 at a certain point in time when the infrared beam source 6 and the beam controller 7 narrow the infrared beam into a narrow beam and irradiate it while scanning in FIG. 1. FIG. In the figure, the shaded area is the liquid crystal property change area 1) where the optical properties of the liquid crystal 2 have changed, and the black dot near the center of the liquid crystal property change area 1) is the infrared beam that is irradiated with a narrow infrared beam. This is the irradiation point 12. Since the size of the liquid crystal property changing area 1) is proportional to the amount of heat generated at the infrared beam irradiation point 12, the infrared beam is scanned while measuring the size of the liquid crystal property changing area 1), and the size of the liquid crystal property changing area 1) is determined. If the brightness is modulated and displayed in proportion to the temperature, a heat generation distribution map can be obtained.

Furthermore, when the heat generation distribution on the surface of a semiconductor device is inspected by pulsed infrared beam irradiation, a diagram showing changes in the optical characteristics of the liquid crystal at a certain point in time is similar to FIG. 3. However, in this case, the infrared beam is irradiated in a pulsed manner, so the size of the liquid crystal characteristic change area 1) or the rate at which the size increases after a certain period of time from the start of irradiation is measured, and this measured value is used as the brightness. If an image is created using the scanning position of the infrared beam as a signal and the positional information of the heat generation distribution, it can be obtained from a heat generation distribution map. In the case of infrared beam irradiation,
Although it is possible to obtain a heat generation distribution map with a single infrared beam scan, it is possible to reduce errors in measurement values and obtain a more accurate heat generation distribution map by overlapping heat generation distributions obtained through multiple scans. is also possible.

〔Effect of the invention〕

As explained above, the present invention has the advantage that in a method of inspecting the heat distribution on the surface of a semiconductor device using a liquid crystal, the heat distribution can be accurately, efficiently, and economically inspected by using infrared light in combination. be.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of an inspection apparatus for carrying out the inspection method of the present invention. Figures 2 (a), (b), (C1 and Figure 3 are schematic diagrams showing examples of inspection results, respectively. 1... Semiconductor device, 2... Liquid crystal, 3... Drive circuit, 4... ... Constant temperature bath, 5... Infrared light source, 6... Infrared beam light source, 7... Beam control section, 8... Light source microscope, 9... Image storage device, 10... Image processing device , 1)...Liquid crystal characteristic change area, 12...Infrared beam irradiation point. , hawk,'・-・ji' Example 7 fi1 (21 (α) Fu, Kabuto (b) (c) Case 2

Claims (4)

[Claims] (1) In a method for inspecting a semiconductor device, which involves uniformly applying liquid crystal to the surface of the semiconductor device and inspecting the heat generation distribution on the surface of the semiconductor device by utilizing the fact that the optical characteristics of the liquid crystal change at a specific temperature, the method includes: A method for inspecting a semiconductor device, comprising inspecting the heat generation distribution while irradiating the surface of the semiconductor device with infrared rays. (2) The method for inspecting a semiconductor device according to claim (1), wherein the surface to be measured is uniformly irradiated with infrared rays. (3) The method for inspecting a semiconductor device according to claim (1), in which the infrared rays are focused into a narrow beam and irradiated while scanning. (4) The method for inspecting a semiconductor device according to claim (1), in which infrared rays are irradiated in a narrow beam-like pulsed manner.