Electric heating – Microwave heating – With diverse device
Reexamination Certificate
2000-12-14
2001-08-21
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With diverse device
C219S678000, C219S702000, C438S057000
Reexamination Certificate
active
06278097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of burning in a semiconductor device used in a microwave region, particularly in a region at a frequency of not less than 1 GHz.
2. Description of the Related Art
While compound semiconductors such as GaAs are used for transistors used in microwave regions (several hundreds of MHz to 100 GHz), particularly in high-frequency region at a frequency of not less than 1 GHz, such compound semiconductors have various energy levels on the surface and inside. Some of these levels experience chronic changes such as diminishing concentrations due to electric stress given to the transistor, and therefore a burn-in process is carried out wherein electric stress is given to the transistor to cause changes beforehand in order to ensure reliability of the transistor.
FIG. 14
is a schematic diagram of a burn-in apparatus of the prior art. In the drawing, reference numeral
1
denotes a transistor,
2
denotes a package, and
3
denotes a matching circuit at the operating frequency. The semiconductor device being burned in is an internally matched FET having a matching circuit incorporated in the package.
Burn-in is carried out, with a predetermined drain voltage being applied to a transistor
1
, by amplifying a frequency signal (for example 20 GHz) which is output from a signal source
5
by means of an amplifier
7
. The signal is supplied to a gate of the transistor
1
while maintaining this state for a predetermined period of time and monitoring the power of the input and output microwave signal by means of a power monitor
6
.
During such a burn-in operation, unless frequency matching is accurately done, a reflected wave is generated due to the parasitic inductance and capacitance of jigs and wirings, thus making it impossible to feed high-frequency signals to the transistor, and consequently it becomes difficult to carry out such matching in high-frequency region not lower than 1 GHz. Also it becomes necessary to fabricate wiring of the matching circuit with a high dimensional accuracy in order to match the impedance. This results in higher cost of the matching circuit itself and higher total cost including peripheral devices such as the amplifier.
Meanwhile the present inventors have found that, while burn-in is carried out with a high-frequency electric stress applied, the effect of burn-in may also be achieved by using a frequency lower than the operating frequency, that the impurities do not respond to frequencies lower than a certain value and are mobilized thus making it impossible to achieve the same burn-in effect as that carried out at the operating frequency.
That is, because impurities have different response frequencies (reciprocal of response speed), the impurities cannot follow the changes in the electric field and move accordingly in the case of burn-in with an alternating electric field of a frequency higher than the response frequency of the impurity level. When the burn-in frequency is set lower than the response frequency, however, the impurities move in a behavior different from that observed during burn-in at the operating frequency where the impurities do not move, thus the desired burn-in effect cannot be achieved.
According to the inventor's knowledge, the frequency at which the impurities at the impurity level begin to move is 100 MHz or lower for semiconductors such as GaAs, and the physical behavior of impurities remains the same whether the frequency is 1 GHz or 100 GHz, if the frequency is higher than 100 MHz.
At a frequency higher than 100 MHz, thermal effects can be prevented because this frequency is sufficiently higher than the transient thermal response frequency of semiconductor which is several megahertz.
Based on the finding described above, it is assumed that a burn-in effect similar to that achieved at the actual operating frequency, for example 18 GHz or 40 GHz, can be obtained by burning in-at a frequency higher than 100 MHz.
Japanese Patent Kokai Publication No. 60-33066 discloses a method of burning in by applying a low-frequency signal (10 MHz or lower) to a gate electrode of a high-frequency transistor. However, because impurities at the impurity level begin to move at a low frequency, such as 10 MHz or lower, it will not be possible to achieve the same burn-in effect as that obtained with the operating frequency (100 MHz to 20 GHz).
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of producing a semiconductor device having the same burn-in effect as is achieved by burning in at the operating frequency, through burn-in at a frequency lower than the operating frequency of a high-frequency transistor.
The present invention provides a method of burning in semiconductor transistors by supplying a signal of burn-in frequency to the semiconductor transistors used in a microwave region, wherein the burn-in frequency is set lower than the operating frequency of the semiconductor transistor device and is higher than the response frequency of the impurities included at the impurity level.
By employing such a method as described above, the same burn-in effect as is achieved by burning in at the operating frequency can be achieved, even when burn-in is carried out at a frequency lower than the actual operating frequency (microwave region from several hundreds of mega-hertz to 100 GHz).
The burn-in frequency is preferably higher than the transient thermal response frequency of the semiconductor transistor.
This is because, when burned in at a frequency higher than the transient. Thermal response frequency, heat due to transient thermal response is not generated during burn-in process and therefore burn-in condition can be prevented from changing.
The operating frequency is preferably higher than 1 GHz.
This is because it makes it possible to burn in a semiconductor transistor of a high operating frequency at a lower burn-in frequency.
The burn-in frequency is preferably selected from the range from 10 MHz to 1 GHz.
The burn-in frequency is more preferably selected from the range from 100 MHz to 1 GHz.
The semiconductor transistor device may also consist of an input matching circuit for the operating frequency, the semiconductor transistor and an output matching circuit for the operating frequency.
The burn-in operation may also be done by connecting an input/output matching circuit for the burn-in frequency to the semiconductor transistor device.
The semiconductor transistor may also be put in class A operation by using a resistor R for the load of the output matching circuit.
This is because such a method enables it to burn in a semiconductor transistor used in class A operation.
The semiconductor transistor may also be put in class C operation by using a resistor R and an LC parallel circuit which is connected in parallel with the resistor R and resonates at the burn-in frequency for the load of the output matching circuit.
This is because such a method enables it to burn in a semiconductor transistor used in class C operation.
The semiconductor transistor may also be put in class F operation by using a resistor R, a first LC parallel circuit which is connected in parallel with the resistor R and resonates at the burn-in frequency and a second LC parallel circuit which is connected in series between the resistor R and the first LC parallel circuit and the transistor output and resonates at a frequency three times the burn-in frequency, for the load of the output matching circuit.
This is because such a method enables it to burn in a semiconductor transistor used in class F operation.
The present invention also provides a burn-in apparatus for burning in the semiconductor transistor used in microwave region by supplying a signal of burn-in frequency, comprising a burn-in frequency signal source, a semiconductor transistor device with an input connected to the signal source, and a load connected to an output of the semiconductor transistor device, wherein the burn-in frequency is lower than the operating frequency of the
Leung Philip H.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Burn-in apparatus for burning-in microwave transistors does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Burn-in apparatus for burning-in microwave transistors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Burn-in apparatus for burning-in microwave transistors will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2434979