JP2007263575A - Method and apparatus for inspecting semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for inspecting a semiconductor device preventing overkill itself. <P>SOLUTION: In the method for inspecting the semiconductor device mounting the plurality of semiconductor devices on an inspection socket in order, inspecting electrical characteristics to accumulate inspection data for each semiconductor device, and grading the quality of the inspected semiconductor devices on the basis of the inspection data, wherein the inspection of the electrical characteristics includes a contact test, the method includes a step of accumulating a measurement value in the contact test of the semiconductor device that has passed the contact test, a step of generating an arithmetic value from the accumulated measurement value of the contact test, and a step of predicting failure of the inspection socket by comparing a predetermined reference value with the arithmetic value obtained by the measurement value of the contact test. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical inspection method for a semiconductor device, and more particularly to a semiconductor device inspection method related to a test socket defect of a tester to which a semiconductor device under test (Device Under Test; hereinafter referred to as DUT) is mounted. And an inspection apparatus.

  The tester is an automated apparatus in which hardware and software having a function of electrically inspecting a semiconductor element are combined. In general, since semiconductor devices have a tendency to increase the number of pins, a tester and a DUT are connected via an inspection socket. In the inspection of the electrical characteristics of the semiconductor device, a contact test is first performed for whether there is continuity between the DUT and the tester via the inspection socket. If a pass (or called Pass) is not obtained for this test item, the subsequent test items are not executed and are determined to be defective. However, among those defective products, the above-described inspection socket was caused as a cause (for example, deterioration of the inspection socket terminal or poor conduction due to the deposit on the terminal), and it was erroneously determined as defective. Things could have been included too. In other words, there was a possibility that a good semiconductor device was wasted.

Therefore, as in Patent Document 1 and Patent Document 2, the results of the contact test are accumulated in the tester, and when the frequency of occurrence of defects in the contact test exceeds a certain standard, the semiconductor device is supplied to the socket. As a result, wasteful disposal of non-defective semiconductor devices (hereinafter also referred to as “Overkill”) is avoided, and wasteful disposal is reduced.
JP 2000-162273 A JP 2004-317513 A

  However, in the case of Patent Document 1 and Patent Document 2, since the inspection is still continued until a certain frequency occurs after actually starting the contact failure, there is a limit to reducing Overkill.

  It is an object of the present invention to provide a semiconductor device inspection method and inspection apparatus that solve the above-described problems and prevent Overkill itself.

  In order to reduce Overkill, it is necessary to find a test socket in a defective state as early as possible. Therefore, the results of the contact test performed at the beginning of the electrical characteristic inspection were collected, and it was examined whether the quality of each inspection socket could be predicted from the tendency of those results. As a result, only the measurement values in the contact test of the semiconductor device to be inspected passed in the contact test are stored in the storage means in the tester, and the current measurement is repeated multiple times from the accumulated measurement value. If the measured value reaches this reference value (this reference value is within the pass judgment value in the contact test, but higher than the value at the start of tester use), It turned out that it would be good to be able to stop using the inspection socket.

The present invention has been made based on the above findings, and the features thereof are as follows.
(1) A method of inspecting a semiconductor device according to the present invention includes mounting a plurality of semiconductor devices in an inspection socket in order, inspecting electrical characteristics, accumulating inspection data for each semiconductor device, In the method of inspecting a semiconductor device for selecting pass / fail based on inspection data, the inspection of the electrical characteristics includes a contact test, and a step of accumulating measured values in the contact test of a semiconductor device that has passed the contact test; And a step of generating a calculated value from the accumulated measurement value of the contact test, and comparing the predetermined reference value with the calculated value obtained from the measurement value in the contact test to determine whether the inspection socket is defective And a step of predicting.
(2) In the above (1), when a defect in the inspection socket is predicted, the method further includes a step of displaying the fact.
(3) A tester for a semiconductor device according to the present invention is a test socket on which a semiconductor device is mounted, storage means for storing a measurement value in a contact test, and reading a measurement value in the contact test from the storage means, A calculation value generating means for generating a calculation value; a prediction means for comparing a calculation value obtained from a measurement value in the contact test with a predetermined reference value; and predicting a defect of the inspection socket; Signal generating means for generating a signal for stopping the use of the inspection socket whose failure is predicted by the predicting means.

  According to the present invention, since it is possible to predict and deal with a defect in the inspection socket, it is possible to prevent a good product of the semiconductor device from being erroneously determined as a defective product. In addition, it is possible to suppress a decrease in yield due to Overkill.

  As an embodiment according to the present invention, a method for inspecting a CMOS semiconductor device will be described. In the contact test, the power supply pin and the GND pin are fixed to 0 V, the voltage when a current of several tens to several hundreds of μA is applied to each terminal pin of the semiconductor device, and the absolute value of the value is If it is within the range of the minimum forward voltage VminL and the maximum forward voltage VmaxL to be determined, the contact test is determined to be Pass. In addition, it is assumed that the socket before the start of inspection is sufficiently cleaned and no contact failure occurs. FIG. 1 is a flowchart for explaining an electrical inspection method for a semiconductor device according to the present embodiment. The following description is performed along the flowchart of FIG. 1, and the order of the steps to be performed is performed in the order of numbers (1) to (8).

  (1) First, an inspection apparatus in a ready state in which a handler and a tester are combined is set up.

  (2) Next, the DUT is installed by the handler in the inspection socket on the DUT board of the tester (S1001).

  (3) Next, an inspection program is operated by a tester to start an inspection of electrical characteristics for the DUT on the DUT board. First, a contact test is performed (S1002).

  (4) A pass / fail judgment of the contact test is performed (S1003). If the contact test fails (hereinafter also referred to as “fail”), the DUT being inspected is discarded, and the next semiconductor device is inspected (S1013). If the contact test is Pass, the total number N of Pass and the absolute value Vm (N) of the measured voltage value at that time are stored in the storage means provided in the tester (S1004). The storage means in this case was a built-in hard disk in terms of capacity and access speed.

(5) Select the measured values (from Vm (N) to Vm (N-9)) that go back 10 times from the current examination, and calculate the calculated value Vav (N) from these measured values using the formula of a) To do. If the number of inspections N is less than 10, the equation of b) is used. In any case, N represents an arbitrary integer (S1005).
a) When N ≧ 10
Vav (N) = {Vm (N) + Vm (N-1) + Vm (N-2) + Vm (N-3) + Vm (N-4) + Vm (N-5)
+ Vm (N-6) + Vm (N-7) + Vm (N-8) + Vm (N-9)} / 10
b) N <10
Vav (N) = {Vm (N) + Vm (N-1) + Vm (N-2) + Vm (N-3) +… + Vm (4) + Vm (3) + Vm (2) + Vm (1)} / N
The calculation value Vav (N) is calculated by calculation value generation means provided in the tester. More specifically, it is performed by a software method under the control of an inspection program provided in the tester.

(6) The calculated calculated value Vav (N) is compared with a predetermined reference value VC to predict a failure of the inspection socket (S1006). Specifically, the determination is one of the following a), b), or c).
a) When N = 1, it is determined that a failure of the inspection socket is not predicted.
b) If N> 1 and Vav (N)> VC, it is determined that a failure of the inspection socket is predicted.
c) When N> 1 and Vav (N) ≦ VC, it is determined that a failure of the inspection socket is not predicted.
Here, the reference value VC and Vcent used to create the reference value VC are calculated by the following equations.
VC = Vcent + {(VmaxL−Vcent) / 2}
Vcent = (VminL + VmaxL) / 2

  As described above, the arithmetic average of the measurement values in the inspection that is a predetermined number of times after the current inspection is adopted as the calculated value, and by comparing this with the reference value, it is possible to reliably determine the defect of the inspection socket. That is, it is possible to reliably detect the deterioration of the contact state of the inspection socket while avoiding the influence of variations due to measurement errors.

  If it is determined in S1006 that a failure of the inspection socket is predicted (in the case of b), the failure determination is transmitted to the handler. The microprocessor of the handler that has received the failure determination controls the hardware inside the handler to stop using the socket in the defective state (S1016). On the other hand, when the failure of the inspection socket is not predicted (in the case of the above a) or c), the inspection of other electrical characteristics is continued as it is (S1007). The calculation of Vcent used for the creation of the reference value VC, the calculation of the reference value VC, the comparison between the calculated value Vav (N) and the reference value VC, and the prediction prediction of the failure are performed by a prediction means provided in the tester. . More specifically, it is performed by a software method under the control of an inspection program provided in the tester.

  (7) Next, the electrical test results are collected by the tester and stored in the result storage means provided in the tester (S1008). A series of operations for collecting the inspection results of the electrical characteristics and storing them for each DUT in the result storage means provided in the tester is performed in software within the inspection program. Note that the above-described electrical characteristic inspection results include a function inspection result, a leakage current inspection result, a timing inspection result, and the like. For reference, in the electrical inspection of semiconductor elements, detailed inspection results for all inspection items are recorded and stored in the result storage means of the tester.

  (8) Next, the pass / fail of the DUT is determined from the inspection result of the electrical characteristics accumulated in the result storage means (S1009). The determination result is stored in the result storage means of the tester for each DUT together with the measurement result of the electrical characteristics collected and stored so far. Thereafter, classification data for determining pass / fail is transmitted to the handler. The handler that receives the classification data for determining pass / fail from the tester physically performs a process of classifying the DUT that has been inspected under the control of the internal microprocessor. The DUT determined to be unacceptable is moved to an area to be discarded by the handler (S1019). The determination of pass / fail of the DUT is performed by a software method under the control of an inspection program provided in the tester.

  According to the above inspection method, by managing the inspection history of the semiconductor device that has passed, it is possible to predict a defect in the inspection socket within the range of the minimum forward voltage VminL and the maximum forward voltage VmaxL that are determined as non-defective products. Can do. As a result, it is possible to reduce the overkill of the semiconductor device as much as possible, and further, since it is not necessary to perform an extra inspection, the time and labor can be shortened.

  In this embodiment, in S1016, the hardware inside the handler is controlled to stop the use of the defective socket, but before that, the test socket is cleaned and replaced by the operator from the tester. A program for issuing a warning to prompt may be provided.

  The storage means for storing the absolute value Vm (N) of the measured voltage value and the result storage means for storing the inspection result may be either the same area (or apparatus) or another area (or apparatus). These may be appropriately selected according to the amount of data to be stored and the conditions of the tester device. In addition, the storage unit and the result storage unit do not necessarily have to be built in the tester, but may be electrically connected to the tester and exchange data. That is, an external hard disk drive may be prepared and connected to a tester.

  Further, in the present embodiment, the storage means is a hard disk, but by other storage means (memory such as RAM and ROM, MO, media that can be written and rewritten such as recordable CD and recordable DVD). Also, the effects of the present invention are exhibited.

  In the above (5), the average value for the maximum 10 times going back from the measurement time point is calculated as the calculation value, but the number of times related to calculation value calculation in the present invention is not limited to this. What is necessary is just to select the frequency | count of calculation value calculation suitably by the kind of DUT package, the number of pins, the usage frequency of the socket for an inspection, etc. Similarly, the calculation method of the reference value in (5) and the determination condition in (6) can be appropriately set according to the type of DUT package, the number of pins, the usage frequency of the inspection socket, and the like.

5 is a flowchart for explaining a semiconductor device inspection method according to an embodiment of the present invention;

Claims (3)

A semiconductor device inspection method in which a plurality of semiconductor devices are sequentially attached to an inspection socket, electrical characteristics are inspected, inspection data is accumulated for each semiconductor device, and inspected semiconductor devices are selected based on inspection data. ,
The inspection of the electrical characteristics includes a contact test,
A step of accumulating measured values in the contact test of the semiconductor device that has passed the contact test;
Generating a calculated value from the measured value of the contact test;
A method for inspecting a semiconductor device, comprising: comparing a predetermined reference value with a calculated value obtained from a measured value in the contact test to predict a defect of the inspection socket. 2. The method for inspecting a semiconductor device according to claim 1, further comprising a step of displaying the fact when a defect of the inspection socket is predicted. An inspection socket in which a semiconductor device is mounted;
A storage means for storing the measured values in the contact test;
Read out the measured value in the contact test from the storage means, to generate a calculated value, calculated value generation means,
A prediction means for predicting a defect of the inspection socket by comparing a predetermined reference value and a calculated value obtained from a measurement value in the contact test;
A tester for a semiconductor device, comprising: a signal generation unit that generates a signal for stopping the use of the inspection socket in which a failure is predicted by the prediction unit.

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