Abstract:
A high-frequency power amplifier includes: a semiconductor substrate; transistor cells separated from each other and located on the semiconductor substrate; and testing electrodes respectively connected to individual transistor cells, wherein an electrical signal and power to individually operate each corresponding transistor cell are supplied to each transistor cell, independently, from outside, using the testing electrodes.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a high-frequency power amplifier and method for manufacturing the same which can conduct the high-frequency burn-in test efficiently. 
         [0003]    2. Background Art 
         [0004]    In a high-frequency burn-in test, by using equipment (DC power supply, RF stress signal generator, and RF load adjusting equipment such as a tuner) which is mounted on a burn-in device and can adjust an electric stress, a DC stress signal or an RF stress signal is applied to a transistor cell of a high-frequency power amplifier. Conventionally, a high-frequency burn-in test was conducted by applying a stress signal simultaneously to a plurality of the transistor cells connected in parallel (see Japanese Patent Laid-Open No. 01-173761, for example). 
       SUMMARY OF THE INVENTION 
       [0005]    Application of the RF stress signal rather than the DC stress signal can give a stress to a transistor cell in a wider operation region, and a stress effect is greater. However, when a burn-in test is to be conducted by simultaneously operating a plurality of the transistor cells included in the high-frequency power amplifier which is a final product, the transistor cells need to be operated by frequencies and power according to the individual final products. Particularly, a device for high-frequency burn-in testing for a high-frequency power amplifier with a high frequency and large power is expensive, and maintenance management of the device is difficult. 
         [0006]    In view of the above-described problems, an object of the present invention is to provide a high-frequency power amplifier and method for manufacturing the same which can conduct the high-frequency burn-in test efficiently. 
         [0007]    According to the present invention, a high-frequency power amplifier includes: a semiconductor substrate; a plurality of transistor cells separated to each other and provided on the semiconductor substrate; and a plurality of testing electrodes connected to the plurality of transistor cells respectively and individually, wherein an electrical signal and power for individually operating the corresponding transistor cell are supplied to each of the transistor cells independently from an outside by the testing electrodes. 
         [0008]    In the present invention, a plurality of testing electrodes are connected to the plurality of transistor cells respectively and individually, and an electrical signal and power for individually operating the corresponding transistor cell are supplied to each of the transistor cells independently from an outside by the testing electrodes. Therefore, the high-frequency burn-in test can be conducted efficiently. 
         [0009]    Other and further objects, features and advantages of the invention will appear more fully from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a plan view illustrating a high-frequency power amplifier according to Embodiment 1 of the present invention. 
           [0011]      FIG. 2  are diagrams for explaining an operation of the high-frequency power amplifier at burn-in. 
           [0012]      FIG. 3  is a plan view illustrating a high-frequency power amplifier according to Embodiment 2 of the present invention. 
           [0013]      FIG. 4  is a plan view illustrating a high-frequency power amplifier according to Embodiment 3 of the present invention. 
           [0014]      FIG. 5  is a plan view illustrating a high-frequency power amplifier according to Embodiment 4 of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    A high-frequency power amplifier and method for manufacturing the same according to the embodiments of the present invention will be described with reference to the drawings. The same components will be denoted by the same symbols, and the repeated description thereof may be omitted. 
       Embodiment 1 
       [0016]      FIG. 1  is a plan view illustrating a high-frequency power amplifier according to Embodiment 1 of the present invention. A plurality of transistor cells  3  are separated to each other and provided individually on a semiconductor substrate  2  of a high-frequency power amplifier  1 . A plurality of testing electrodes  4  are connected to the plurality of transistor cells  3 , respectively and individually. An electrical signal and power for individually operating the corresponding transistor cells  3  are supplied to each of the transistor cells  3  independently from an outside by the testing electrodes  4 . 
         [0017]    A manufacturing method of this high-frequency power amplifier  1  will be explained. First, the plurality of transistor cells  3  are separated to each other and formed on the semiconductor substrate  2 . Subsequently, the plurality of testing electrodes  4  connected individually to the plurality of transistor cells  3 , respectively, are formed. 
         [0018]    Subsequently, an RF probe  5  in a chip (wafer) state is brought into contact with one of the plurality of testing electrodes  4 , and an electrical signal (a DC stress signal or an RF stress signal) and power are independently supplied from the outside to the corresponding transistor cells  3 , and a high-frequency burn-in test is conducted. In the RF probe  5 , a load circuit  6  corresponding to the RF stress signal is provided. 
         [0019]      FIG. 2  are diagrams for explaining an operation of the high-frequency power amplifier at burn-in. In the figure, a point A is a stress point by the DC stress signal. A point B is a stress range by the RF stress signal. In the high-frequency burn-in test, by applying a stress by the DC stress signal indicated by the point A and by further applying the RF stress signal indicated by the point B, deterioration of a fragile portion of the transistor cell  3  is accelerated, and the transistor cell  3  which will deteriorate is detected. 
         [0020]    In this embodiment, the plurality of testing electrodes  4  connected individually to the plurality of transistor cells  3 , respectively, are provided. Thus, the frequency and load of the RF stress signal can be freely selected for each of the transistor cells  3  to be tested. Therefore, the DC stress signal and the RF stress signal can be made required minimum power signals to apply a stress to one transistor cell  3 , and thus, a stress effect can be obtained with a smaller power signal without depending on the frequency and power of the final product. Moreover, a stress condition can be made common without depending on the frequency and power of the final product. As a result, the high-frequency burn-in test can be conducted efficiently. 
       Embodiment 2 
       [0021]      FIG. 3  is a plan view illustrating a high-frequency power amplifier according to Embodiment 2 of the present invention. As the testing electrode  4 , a plurality of electrodes  4   a ,  4   b , and  4   c  are connected to each of the transistor cells  3 . A plurality of load circuits  7   a ,  7   b , and  7   c  having different loads are connected between the transistor cell  3  and the plurality of electrodes  4   a ,  4   b , and  4   c , respectively. As a result, a type of a stress can be used selectively in accordance with the purpose at RF probing. For example, the load circuit  7   a ,  7   b , or  7   c  having a load according to the frequency of the RF stress signal can be selected. Moreover, a bias voltage of the transistor cell  3  can be set by a resistance value of the load circuit  7   a ,  7   b  or  7   c.    
         [0022]    By using a signal with a higher frequency as the RF stress signal, sizes of the load circuits  7   a ,  7   b , and  7   c  can be reduced. Moreover, if the load circuits  7   a ,  7   b , and  7   c  are resistors, by selecting the resistance value so as to become a desired DC bias point, a desired DC stress signal can be applied without depending on a function of an external DC power supply. 
       Embodiment 3 
       [0023]      FIG. 4  is a plan view illustrating a high-frequency power amplifier according to Embodiment 3 of the present invention. Resistors  8   a ,  8   b , and  8   c  connected between the transistor cell  3  and the corresponding testing electrodes  4   a ,  4   b , and  4   c  are formed. In the high-frequency burn-in test, a condition of the electrical signal is adjusted while a change of resistance values of the resistors  8   a ,  8   b , and  8   c  are measured by a temperature monitor. As a result, a condition of the DCRF stress signals can be adjusted easily during the test. 
       Embodiment 4 
       [0024]      FIG. 5  is a plan view illustrating a high-frequency power amplifier according to Embodiment 4 of the present invention. A black body  9  irradiating infrared light to each of the transistor cells  3  is formed. During the high-frequency burn-in test, the condition of the electrical signal is adjusted while a temperature of the black body, that is, a temperature of the transistor cell  3  is measured by the temperature monitor. As a result, the condition of the DCRF stress signal can be adjusted easily during the test. 
         [0025]    Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. 
         [0026]    The entire disclosure of Japanese Patent Application No. 2014-027810, filed on Feb. 17, 2014, including specification, claims, drawings and summary, on which the Convention priority of the present application is based, is incorporated herein by reference in its entirety.